Abstract: In this paper, the principle of measuring the depth of defects by parallax method is introduced. Through the digital radiography testing with defective workpiece and CIVA simulation, the feasibility of the method is explored and the factors influencing the measurement accuracy are analyzed. Digital radiography technology makes up for the disadvantages of conventional film imaging technology such as low detection efficiency, difficulty in measurement, and large measurement error. At the same time, the verification mark is introduced to accurately verify the measurement result, and the positioning error caused by the operation is avoided.