A spectral responsivity testing system for Ultraviolet2visible has been developed. The system comprises :optical source(dual lamps) ,grating spectrometer and special designed detector housing. The testing principle is based on the tested detector and a reference detector are tested under identical conditions. A low noise lock2in amplifier measure tested detector signal as well as the output of a calibrated reference Si detector to obtain the spectral responsivity. The main technical problems emphasized on measuring accuracy and stability of system were solved. The testingresults show that the system has good qualities of stability and easy operation.