Abstract: Existing studies have systematically revealed the effects of factors such as sprinkler disc structure, nozzle diameter, and working pressure on the hydraulic performance of sprinklers. However, the influence of damping grease viscosity on the rotational speed uniformity of rotating-damped sprinklers remains unknown. The rotational speed uniformity of rotating-damped sprinklers plays a crucial role in ensuring stable water distribution and improving irrigation uniformity in sprinkler systems. Rotating speed fluctuations not only lead to uneven water distribution, affecting crop growth, but also reduce water use efficiency. Therefore, an in-depth study of the key factors affecting rotational speed uniformity is of great significance for improving sprinkler performance and irrigation quality. Therefore, the R3000 rotating-damped sprinkler equipped with damping greases of different viscosities is used as the research object, aiming to investigate the influence of damping grease viscosity on the sprinkler’s hydraulic performance, with a focus on the effects of different working parameters and sprinkler disc structures on rotational speed stability, so as to break the foreign monopoly on damping mechanisms and enable low-cost, low-vibration, constant-speed sprinklers to replace low-pressure impact sprinkler products. The sprinklers used in the experiment were equipped with domestic damping grease, improved damping grease No.1 and No.2(where No.1 and No.2 refer to the original domestic damping grease modified by the addition of silica micropowder at mass-volume fractions of 15% and 20%), and imported damping grease. The improved damping grease was developed on the basis of the domestic formulation, in which silica micropowder was incorporated at different concentrations to achieve performance modification and tailoring of the grease’s rheological and viscous characteristics. In Grease No.1 and Grease No.2, the contents of silica micropowder were 15% and 20%, respectively, representing two distinct loading levels intended to tune viscosity and damping behavior across operating conditions. Rotational speed was measured in real time using a Hall sensor, and systematic experiments were conducted under different temperatures, sprinkler disc structures, and working pressures. Experimental results demonstrated that Grease No.2, containing 20% silica micropowder, delivered the best overall performance under a variety of operating scenarios, exhibiting superior rotational-speed stability and comprehensive operational robustness relative to the other formulations. Taking the brown sprinkler disc as an example, under low temperature and low pressure conditions such as 10℃ and 103 kPa, the rotational speed fluctuation ranges for the No.1, No.2, domestic, and imported damped sprinklers were 1.186%-8.503%, 0.075%～1.769%, 0.717%～8.455%, and 0.182%～2.287%, respectively. Notably, the No.2 damped sprinkler exhibited the smallest variation in rotational speed fluctuation, performing closest to the imported sprinkler. In fact, under these specific conditions, its rotational stability surpassed that of the imported sprinkler. Under high temperature and high pressure conditions such as 30℃ and 137 kPa with the brown disc, the rotational speed fluctuation ranges for the same four sprinkler types were 1.252%～9.783%, 0.611%～3.990%, 0.488%～5.476%, and 0.065%～3.574%, respectively. Once again, the No.2 damped sprinkler demonstrated the lowest rotational speed fluctuation and maintained performance most comparable to the imported sprinkler. In summary, these findings confirm that the modifications applied to Grease No.2 fully achieved the intended objectives, and the performance of the No.2 damped sprinkler proved to be optimal. Further analyses of the long-term stability of the No.2 damping grease, domestic damping grease, and imported damping grease under high pressure over extended periods were performed. After continuous operation for 9 hours at a working pressure of 207 kPa, the average rotational speeds of sprinklers equipped with these three types of damping grease were 3.80 r/min, 10.33 r/min, and 4.81 r/min, respectively, with the corresponding average rotational speed fluctuation rates of 3.66%, 10.78%, and 0.97%. Compared with the domestic grease sprinkler, the rotational performance of the No.2 grease sprinkler is closest to that of the imported grease sprinkler. However, compared with the imported grease sprinkler, the rotational speed of the No.2 grease sprinkler is lower due to its slightly higher viscosity. Therefore, to address the high viscosity of Grease No.2 at low temperatures and its viscosity reduction at elevated temperatures, follow-up research can adjust the proportion of silica micropowder and consider introducing new components to optimize stability under high-temperature and long-duration operating conditions.