Abstract: This article discusses the validity of ultraviolet or visible light intensity measurements according to illumination impacts the reliability of fluorescent penetrant testing vitally and the substandard illumination interferes inspectors judgment. We carry out the experimental study from the measured distance and angle. Analyze the different requirements about ultraviolet or visible light illumination of the relevant standards. Eventually confirm the factors affecting ultraviolet or visible light illumination measurements after analyzed the data by lean concept, and producing a special measuring tooling to ensure the quality of penetration testing aiming at components.