Abstract: During the running process of the gas flow line, the inner wall of the elbow was continuously eroded by sand particles, the evolution of surface profile changed continuously and unevenly. Based on the 3D imaging technology, the evolution of surface profile process was accurately described and a CFD method was proposed to study the process. Results show that with the continuous erosion, the severity of wall thickness loss had a larger diffusive velocity toward higher angle direction. The Schiller Naumann drag coefficient model was modified to predict the erosion pattern on the inner wall. These works was of great significance in evaluating the integrity of the piping.