The beam characteristics of semiconductor laser are worse,its beam diver gence angle is larger,and the light spot is oval and uneven,which directly affect t he device coupling efficiency.In order to improve the fiber transmittance and the coupling efficie ncy in the fiber coupling system with high power semiconductor laser,first,the end of fib er is processed by the high precision grinding polishing technology;and then by high laser damage threshold materials choosing and the structure optimization of film system,using electr on-beam vacuum coating and ion assisted deposition,the broadband reflective film is successfully achieved o n the end of multi-mode fiber whose core diameter is 100μm.The test results show that the double-end optical loss of the fiber is reduced by 6% in 900－1100nm band,and the total transmission can be 99.2%.The fiber coupling efficiency of optical fiber coupling system is effectively improved.