A field experiment was conducted to study the effects of applying B,Zn and Mo on seed yield and the number of rhizobia of the Milk vetch in hilly upland red soil.Compared to no B,Zn and Mo fertilizer treatment，applying B,Zn and Mo fertilizer could increase the seed yield of Milk vetch signicantly by 137% to 389%(P＜005)；The main reasons due to the result was the increasing of the number of single plant pod and seed grains per pod,which increased by 189% to 443% and 214% to 333%(P＜005),respectively.Additionally,applying B,Zn and Mo fertilizer could increase the amount of Milk vetch rhizobium by 21% to 824%.The seed yield，economic characters and the number of rhizobium of applying molybdenum fertilizer treatments were better than the one without it，which indicated that the growth condition and seed yield form of Milk vetch was more sensitive to Mo than to B or Zn.