Abstract: Abstract: Winter wheat is one of the main grain crops in North China Plain. The characteristics of field evapotranspiration (ETa) and partitioning the components of ETa serve as the accordance for agricultural water use and management. For a better understand of regulating crop water loss with drip irrigation techniques, field experiments were carried out at Daxing Experiment Base of China Institute of Water Resources and Hydropower Research.Micro-lysimeters (MLS) were selected to measure soil evaporation (Es) of winter wheat with and without straw mulching and treated with three different drip irrigation scheduling. Two positions, under the drip lines (wet zone) and between two drip lines (dry zone), were selected to install the MLS and total 24 MLS was installed in the 12 plots. The MLS was weighed daily and the difference of the two weights was transferred to Es. The accuracy of the MLS was evaluated by comparing the soil water content of inside the MLS to that in the field. Based on the evaluation, the seasonal dynamics of Es over the field was determined and the ratio of Es to ETa was quantified. A semi- experiential model was established to give accuracy estimates of Es.The results showed that MLS with an inner diameter of 10 cm, and a height of 15cm, with changing soil inside MLS every other 5 days, was feasible to give relatively accuracy Es measurements (error<5%) under drip irrigation in the field. After rainfalls (>5 mm), the MLS had to be reinstalled to keep the same of the soil water content inside and outside MLS.Different irrigation amount and mulching treatments affected the Es and Es/ETa significantly. Es and Es/ETa of plots covering plant residuals were significantly lower than those without mulching and, Es and Es/ETa of plots with low irrigation water were significantly lower than those with high and middle irrigation water (P<0.001). The seasonal averages Es were 0.98, 1.13, 1.10, 1.30, 1.02 and 1.22 mm/d for low irrigation water (Ilow) and mulching (M1), Ilow and non-mulching (M0), middle irrigation water (Imid) and M1, Imid and M0, high irrigation water (Ihig) and M1 and IhigM0 treatments, respectively. The seasonal average of Es/ETa were 38.5%, 44.2%, 40.7%, 44.5%, 33.0% and 36.4% for Ilow M1, Ilow M0, Imid M1, Imid M0, IhigM1 and IhigM0 treatments, respectively. Es/ETa of this research were a little higher than some of the ratios from publications, which is partially because of the broader row distance and the lower leaf area index (LAI) of the field. Thus, the drip irrigation needs to be applied together with right agricultural water managements, such as mulching, proper sowing amount and row spaces, to maintain the advantage of this efficient irrigation method.In addition, an easy and feasible model of Es was established by selecting days after irrigation (Dai) as the independent variable. First, to eliminate the effects from the meteorological variables and LAI to Es, we standardized the Es with the potential soil evaporation (Es0), which was calculated with those meteorological variables and LAI by assuming saturate soil water content. In such case, the remaining variable that would influence Es/Es0 (evaporation coefficient, Kes) was soil water content. Then, Dai was selected as an alternative variable of soil water content to make the model more feasible, and an exponential decay to a constant equation was selected to fit the relationship between Es and Dai. Data from Imid treatment was selected to parameterize the model and data from Ilow and Ihig were used to validate the model. Good agreements between the Es estimates and measurements were found in this research, with an average MAE of 0.18 mm/d. With this model, one could get relatively precise estimates of Es under drip irrigation, without measuring soil water content.The results of this research are valuable practically and of scientific significance for selecting high-efficient water-saving irrigation regimes and agricultural water managements for grain croplands in North China Plain and revealing the intrinsic advantages of that regime.