The invention discloses a pullorum agar gel precipitating antigen as well as a preparation method and an application thereof, and belongs to the technical field of veterinarian diagnosis. Salmonella pullorum SP8441 and salmonella pullorum SP9905 are subjected to recovery and passage respectively to form a seed bacterium liquid, then the seed bacterium liquid is inoculated with a solid culture medium for proliferation, after a culture solution is removed centrifugally, bacterial protein is extracted with a lysis buffer, and the pullorum agar gel precipitating antigen is prepared. The technological method is simple, reasonable, scientific, stable in production and low in cost, the prepared pullorum agar gel precipitating antigen product has the advantages of high sensitivity and high specificity, the pullorum purification process can be simplified, the detection application range can be enlarged, and the agar gel precipitating antigen is relatively ideal in pullorum detection.