A miniaturized, widely tunable and fiber-type CW mid-infrared light source system based on DFG/QPM technique is successfully developed. In the system, the segmental tunable fundamental sources are adopted, and the specific tuning bands for the fundamental lights are realized by using electronically controlled optical switches. For pump lasers, three tunable ytterbium doped fiber lasers (YDFLs) whose total tuning bands ranging of 1050～1110 nm are adopted, and for the signal lasers, three erbium doped fiber lasers (EDFLs) with total tuning bands ranging of 1535～1600 nm are selected. A mid-IR DFG laser source module with the size of 440 mm×290 mm×500 mm was successfully developed. And the tuning range of the mid-IR module covers from 3054.5 nm to 4009.1 nm.