Based on the calculation of the MSE of tidal factors,phase lag and zero drift of the digital deformation observation instruments in Guangdong, the continuity, stability and observation quality of the instrument observation data are analyzed and evaluated. The analysis results show that: the observation accuracy of each instrument basically meets the standards of Class I deformation stations of China Earthquake Administration; the ground tilt observation instruments have high accuracy and good stability,especially water pipe inclinometer;the vertical pendulum inclinometer has larger drift and lower data accuracy. The data accuracy of the extensometer and the borehole strain gauge is high;but the drift of borehole strainmeter at Shantou station is large,and the stability of instrument is not as good as that of Xinyi station;the overall quality of observation data from Xinyi and Shantou deformation stations is better than that from Shaoguan station. The deformation observation data of Chaozhou station is disturbed with highly noisy. The stability and accuracy of the data are lower than that from other stations,which indicates that the site condition is one of the important factors to determine the observation quality.