Abstract: To solve the problem of excessive stress caused by thermal expansion caused by high heat treatment temperature of SA-213T91+SA-213TP347HFG dissimilar steel joints,six post weld heat treatment processes for SA-213T91+ SA-213TP347HFG dissimilar steel butt joints were designed.The microstructure and mechanical properties of six sets of different heat treatment processes were compared and analyzed.The results showed that the mechanical properties of the joints under different heat treatment specifications were qualified,which can meet the requirements of process quality manufacturing,The minimum allowable heat treatment specification for this type of dissimilar steel joint was determined to be 715℃/1.5h through simulation,and the heat treatment specification for this type of dissimilar steel butt joint was optimized.This also provides a reference for selecting a reasonable heat treatment temperature during on-site service or repair welding.