The invention discloses a low-pressure casting mold for a box body for a vehicle, and relates to the technical field of aluminum alloy casting. The defects that because the exhaust of the mold is notuniform, the casting partial gas hole, misrun or unclear outline and the like are easily formed are overcome. The low-pressure casting mold comprises an upper mold, a lower mold and a side mold assembly, and further comprises a casting cavity of a sand core assembly, the sand core assembly is fixed on the lower mold through a positioning base, the positioning base is provided with a diversion holecommunicating with the casting cavity, and an exhaust passage is arranged on the upper mold; the sand core assembly communicates with each other, and a main sand core is hollowed out; and an overflowsystem communicating with the casting cavity is arranged on the upper mold. By the technical scheme, balanced exhaust gas in the casting process of the box body can be realized, the gas in the cavityof the casting is rapidly discharged out, and the defects that the casting gas hole, misrun or unclear outline and the like do not exist in the forming box body are overcome, the qualified rate of the products reaches more than 99.9%, and the qualified rate of the formed casting is effectively improved.