Abstract: Ultraviolet light is an important observation tool for fluorescent magnetic tesing and fluorescent penetrant testing, and quality of which has close relationship to the defect detection rate. In accordance with standards GB/T 15882.3—2005 and ASME E1209—1987, in the following specifications: start time, illumination, restart time, voltage fluctuations, effects of temperature, defect detecting ratio in the sun, the influence of strong magnetic field and splash water resistance, the performances of different UV lights made by different manufactures were tested and compared. The testing results could be a guide of selection high-performance UV lamp for the operator.