In recent years,the cascade fluoride fiber laser of both 2 μm and 3 μm wavelengths has the higher application prospects and values in electro-optical countermeasure,laser ranging,laser communication,laser medical and so on,so it has become the research hotspots at home and abroad.The principle and research progress of mid-infrared ZBLAN fiber lasers are introduced from the perspective of doped different rare earth ions.And the faced problems and development directions in the future are pointed out.