An improved method of laser projection photograph to judge the situation of pipeline in service is put forward. The algorithm detects the height of protuberance (which is also called obstruction) through the procedure of track detection which is finished by the combination of laser feature analysis and the comparison method. By Otsu algorithm filtering, parameters of circle are got with least square method. Finally, obstruction height is obtained through obstruction-height table which is calculated off-line. There is no strict light requirement to the pipeline image avoiding the original system’s observation and tests are not synchronous. Three advantages are demonstrated by MATLAB experiments which are obviously better than the original design: higher accuracy, better real-time performance and nice robustness. The average operation time of each frame is less than 0.5 seconds, and the range of height error is 2 mm. Images of almost all situations can be processed through the algorithm.