Abstract: This study focuses on systematically investigating the dynamic characteristics of groundwater level changes and quantifying their dominant controlling factors in the plain area of Jimsar County, a research topic of great significance for arid and semi-arid regions where groundwater serves as a critical water supply source. Such an investigation is fundamental to scientifically and rationally determining groundwater level control indicators, which are core components of the national rigid water resources constraint system aimed at regulating sustainable water use. To achieve this research objective, the plain area of Jimsar County was explicitly designated as the study area, and a comprehensive set of multi-source data were integrated for in-depth analysis, including long-term groundwater level monitoring data spanning 2003 to 2023, detailed meteorological data (e.g., precipitation and temperature), surface runoff data, land use/land cover change data, and human activity intensity evaluation data. Specifically, Kriging interpolation was utilized to map the spatial distribution of groundwater levels, while trend analysis was applied to capture the temporal evolution patterns, thereby comprehensively characterizing the spatiotemporal variations of groundwater level; wavelet coherence analysis was employed to explore the time-frequency correlation between groundwater level changes and hydrometeorological factors, bivariate spatial autocorrelation was used to examine the spatial coupling relationship between human activities and groundwater level variations, and the human activity intensity index method was adopted to assess the degree of human disturbance, collectively revealing the driving mechanisms of groundwater level changes; additionally, a geographical detector model was applied to quantify the individual and interactive contribution of each influencing factor to groundwater level dynamics. The results indicated that the intra-annual dynamic variation of groundwater level in the study area was predominantly dominated by an exploitation-driven pattern, closely associated with the seasonal characteristics of agricultural irrigation. Meanwhile, the long-term groundwater level showed an overall fluctuating downward trend, which could be clearly divided into four distinct stages: a relatively stable fluctuating variation stage (2003–2008), a rapid and significant decline stage (2009–2014), a slight recovery and upward trend stage (2015–2017), and a reversion to a gradual downward trend stage (2018–2023). Across different time scales, significant resonance periods (ranging from 10 to 14 months) and obvious time-lag effects were observed between groundwater level changes and precipitation/runoff, presenting a significant positive correlation; the phase angle ranging from 0° to 60° further suggested that groundwater level changes lagged behind precipitation and runoff changes by approximately 0–2 months. From 2003 to 2023, with the gradual expansion of cultivated land area driven by agricultural development, regions with high-intensity human activities showed a continuous expansion trend, and a distinct local spatial autocorrelation existed between human activity intensity and groundwater level changes, indicating a strong spatial coupling between human disturbance and groundwater evolution. Additionally, the dynamic changes of groundwater level were mainly influenced by multiple factors including surface runoff, human activities, precipitation, and land use types; notably, the interactive effects of these factors exerted a more significant synergistic impact on groundwater level dynamics compared to their individual effects. The findings of this study not only contribute to deepening the understanding of the dynamic response mechanisms of groundwater systems in arid areas but also provide important theoretical support and practical technical references for formulating scientific and reasonable regional groundwater control indicators and realizing the long-term sustainable development and utilization of groundwater resources.