A test method of phase change heat in salt bath of a metallic material belongs to the field of material heat processing. In the test method for isothermal phase change heat of a salt bath quenching metallic material, a temperature-time change curve of the metallic material is firstly drawn in salt bath process, simultaneously, a temperature increase-time curve of salt bath medium is drawn in the salt bath process, the deformation characteristic pint of the cooling curve is ensured by using the releasing characteristic of phase change heat after rapid cooling, and the phase change beginning and phase change ending time and temperature drop of the metallic material are determined according to the characteristics of cooling curve deformation. The heat exchanges of the metallic material and the salt bath medium in the complete process are calculated according to the temperature rise of the salt bath medium, the quality of the salt bath medium and the heat capacity of the salt bath medium in the complete process; the non-phase change heat brought by the metallic material is calculated according to the weight, heat capacity and temperature drop of the metallic material, and the difference between the two parts of heat is the heat phase heat of the metallic material. The method has the advantages of simple and easy operation as well as high accuracy by testing the phase change heat in the salt bath process of metallic material in experimental method.