Based on the study of CWDM and wavelength conversion technology,OTU module applicable to CWDM system is designed. The module supports an eight-channel of CWDM and works in a state of multi-rate. The module has 3R function to ensure the quality of the signal conversion,and high speed data and clock signal are output and can be used as performance monitoring. Experimental results show that the module successfully realizes the conversion of wavelength with better stability and practicability.