Basing on the dynamic observation data of water level in 6 wells in Middle and South Yunnan,we calculated the dynamic process of amplitude and phase difference of water level solid tide and analyze the effect degree of regional stress field on the well-aquifer system so as to provide the reference to explain the decline mechanism of the water levels from tectonic activity.The results show that the amplitudes and phase difference of water level did not change significantly in the decline process of water levels in Yimen,Gaoda,Jianshui and Kaiyuan wells,which cannot prove that the decline of water level was influenced by the regional tectonic stress (strain),so it was mainly caused by the decrease in precipitation supply.The abnormal variation of amplitudes and phase difference of water level were obvious in Xinping and Yuanjiang wells,so the well-aquifer system might be influenced by regional stress field,and the influence of precipitation decreasing cannot be ruled out.