The invention discloses a recombinant strain for Brucella abortus. The recombinant strain for the Brucella abortus is a bacterial strain obtained by killing encoding genes of cold shock protein in the Brucella abortus. Compared with an original strain, the obtained strain has virulence lower than that of the prior vaccine S19, and can be used as a vaccine to immunize animals without killing the genes. By utilization of the strain to immunize a mouse, whether a strain separated from the body of a sicken animal is a vaccine strain or a wild strain can be identified by the PCR method. The modification of the brucelliasis vaccine and the research of a diagnosis and identification agent have important significance in developing a brucelliasis gene deletion marker vaccine and a matched diagnosis and identification agent and promoting the elimination and purification of brucelliasis of the animals all over the world.