Abstract: For the liquid penetration inspection of nuclear power project, the paper shows us the detection principle, key control points such as the choice of penetrant materials, the surface condition of the work-piece, correction and detection technology in low temperature as well as in high temperature, and the time when the requirements for quality control test results evaluation can be put forward, etc. In view of the differences in the results evaluation, the differences of detection units and test personnel were analyzed. The paper put forward the control of the detection time, the strengthening the process control as well as the detection results. The paper also points out that it is significant to distinguish corresponding displays in order to easily determine the shape and nature of defect. For densely displayed small defects, the defect properties should be clearly understood to reduce the difference. As for the inconsistent phenomenon found on the detection, return-to-zero processing opinion is suggested. The above-mentioned measures can help to improve the detection efficiency and to reduce differences, so as to promote technological progress and specification testing.