Based on the observed data of groundwater monitoring wells during the past 20 years, using the method of Mann-Kendall to carry out trend analysis for the groundwater depth series, and selected the typical observed wells to analyze the change in year and years for different area and different periods. The results showed that:the regional groundwater level was evidently declining. From the 1980s to now, the type of dynamic change of groundwater level was gradually transformed from the hydrology-irrigation type to the exploitation type. The exploitation was enhanced. The most obuious area was Pingchuan Zone, especially after 2000. Water delivery to downstream was the main factor leading to the groundwater table decline.