Abstract: In recent years, groundwater levels in parts of the Sanjiang Plain has continuously decreased, which attracts great attention from scholars and related departments. In order to find out the temporal and spatial evolution of the groundwater flow field in the Sanjiang Plain and reveal its main influencing factors, in this paper the ArcGIS interpolation analysis, grid algebraic operations, comparative analysis and other methods are used to analyze the 72 groups of data in the Sanjiang Plain in 1980 and 1092 groups of groundwater level data and 44 groups of national groundwater monitoring data in the same period in 2019 and 2020. The spatio-temporal evolution characteristics of the groundwater flow field in the Sanjiang Plain are ascertained, and the control effects of different influencing factors on the smooth evolution of groundwater are clarified. The results show that, compared with 1980, the groundwater levels of the Sanjiang Plain showed an overall decreasing trend. The groundwater levels of the western plain area cumulatively decreased by 1 to 5 m, with an area of 2.6×10⁴ km², and most areas of the eastern Jiansanjiang reclamation area fell greater than 5 m with an area of 1.17×10⁴ km². Among them, the area where the cumulative drop of groundwater levels is greater than 10 m is as high as 3 400 km², and the average annual drop of groundwater levels is about 0.29 m. Groundwater exploitation causes the changes in the groundwater flow field, and the hydrogeological conditions of "West Sand and East Stick" promote the temporal and spatial evolution of the regional groundwater level decline. The continuous expansion of the scale of paddy fields has caused over-exploitation of groundwater. The shallow surficial clay layer blocks replenishment from rainfall infiltration, and the groundwater cannot achieve self-balance with abundance to compensate for the shortage, resulting in the continuous decline in groundwater levels in the Jiansanjiang Reclamation Area. The results of this research lay a foundation for further investigation of the groundwater change laws and current characteristics of the Sanjiang Plain, and also provide technical support for scientifically guiding the rational development, utilization and management of groundwater resources.