Abstract: Based on the practical requirements of nuclear power plants for wear measurement of control rod guide card and video inspection of screw locking cap, this paper proposed a corresponding video inspection scheme by analyzing the internal and external structures and inspection environment of control rod guide tube, developed a control rod guide card wear measurement device and a screw locking cap video inspection device, studied the machine vision measurement techniques of control rod guide card, and successfully applied it to the in-service inspection of nuclear power plants, directed the replacement of CRGT with severe wear.