By analyzing the changing trends of borehole tilt observation data from October 2001 to May 2015 in Lanzhou,we found that due to the base tray being not installed,there is a trend of drift for long term observation data. After using parabolic function for fitting tendency of the borehole tilt observation data of Lanzhou,we found that the fitting residual error of the borehole tilt observation data in Lanzhou has certain abnormal variations before the three strong earthquakes in the Lintan-Tanchang fracture. We believe that the borehole tilt observation data in Lanzhou can well monitor the moderate earthquake activities in the Lintan-Tanchang fracture,and can provide the basis for earthquake prediction of the Lintan-Tanchang fault zone in the future.