Abstract: In order to study the effect of adjacent well casing on well trajectory description,the impact of casing at different tilt angles,distances and azimuths on inclinometer data was studied.In the experiments,inclinometer was used to record the casing azimuth data,azimuth distortion value was used to characterize the azimuth deviation state and trend,and the data distortion pattern was determined.Experimental results showed that:the serious azimuth distortion caused by vertical casing was within 0.9 m,when the relative azimuth angle was 0°-180°,azimuth distortionwas positive,when the relative angle was 180°-360°,the distortion was negative;the scope of azimuth distortion caused by deviated well was similar to horizontal well,serious distortion region was within 1.5 m,when the azimuth was within the range of 0°-120° and 300°-360°,azimuth distortion was positive, when the azimuth angle was 120°-300°,the distortionwas negative.The study showed that:azimuth distortion value might reflect magnetic interference caused by adjacent well,and the study provided technical support for well trajectory description and correcting in the presence of adjacent well.