It is researched that the intergranular corrosion behavior of composite plates, with low alloy steel and stainless steel, for pressure vessel after hot working. The intergranular corrosion characteristics after hot working for three common stainless steels 304 ,321 and 316 L have been discussed. The results show that composite plates after explosive cladding, microstructure of 321 steel shows a pitting corrosion characteristic, but has a little step structures, the structures of 304 steel is obvious types of intergranular corrosion, and need to improve by heat treatment; Moreover, that character of 316 L steel is most serious, the processes of heat treatment is need reduce. The process of 321 steel, heat treatment is not excess, which would cause intergranular corrosion, but the tendency of intergranular corrosion for 321 is lighter than 316 L. Effects of heat treatment on 304 steel are obvious, intergranular corrosion tendency is the most seriously in three steels after hot working. Steel with more alloy elements (321 , 316 L ) , the heat treatment is lower sensitive than mild steel after heat treatment at sensitizing temperature, therefore, for mild stainless steel ( 304 ) , intergranular corrosion characteristics has little obvious if heat treatment has strictly controlled. The heat treatment of mild stainless steel has significant effects, hot working process can have more effects of intergranular corrosion tendency.