The invention relates to a rough type Brucella melitensis attenuated strain and a vaccine thereof. The rough type Brucella melitensis attenuated strain RM57 is screened by using an antibiotics and M factor serum combined domesticating and screening technology. The safety of the rough type attenuated strain is remarkably improved, but the favorable immune effect for Brucella melitensis is stilled retained. If the attenuated strain is prepared into a Brucella melitensis vaccine, the situation that a Brucella melitensis vaccine immunized animal and a wild strain infected animal are difficult to distinguish is changed, and the safety of the existing vaccine is effectively improved.