The plain in the central Jilin with Changchun and Siping as the center is not only a most developed area in the province, but also a base of producing commodity grain in China. Because of the vast quantity of water usage in city life, industry and agriculture, the conflict between water supply and demand have become more and more prominent. Therefore, understanding exactly the actual situation of groundwater exploitation in this area is crucial to plan the water use in the future. Based on ground water level data of more than one hundred observation wells in recent 10 years, this paper systemically analyses the perennial change laws of water table in the area. Furthermore, the paper puts forward a method to judge whether groundwater in the area is over-draft in the case of no groundwater level depression, and offers some scientific advices on planning water use in the future.