This paper is the result of groundwater survey engineering. [Objective] The study on the temporal and spatial law of groundwater under changing environment is helpful to the fine management of water resources and the guarantee for regional water resources security. [Methods] Based on the rainfall data of typical weather stations in the Huaibei Plain from 1953 to 2019, the wavelet analysis and M-K test method was used to study the periodic changes and trend of rainfall on a multi-year scale. Combined with 395 national monitoring wells and groundwater monitoring data, the principal components analytical method was used to optimize the evaluation of monitoring wells. [Results]The results show that the rainfall in Huaibei Plain appears multiple temporal and spatial scales variation characteristics: The shallow groundwater level has declined continuously in the northwest, while fluctuated greatly in the other regions; In 1970, 2003 and 2019, the shallow groundwater level in the southern region decreased firstly and then recovered, and on the contrast, the shallow groundwater level in the northern region increased firstly and then decreased; The groundwater level in the study area has generally declined; And since 2000, the water level has somewhat risen; The 277 monitoring wells (221 water wells and 56 natural resource wells) optimized by principal component analysis can represent the overall water level changes of 395 original national monitoring wells. [Conclusions] The long-term monitoring data of the national groundwater monitoring project can well serve the evaluation and management of water resources at the basin scale, but still need to be optimized and densified at the provincial, municipal scales or key areas. The artificial observation in unified time period can also make up for this deficiency which should be densified in the high hydraulic gradient areas such as both sides of important rivers and lakes, the north bank of Huaihe River, and the piedmont plain in the northeast.