The common pre-tightening methods used in ANSYS finite element analysis of combination frame body were introduced. Aiming at 5000 kN press, the pre-tightening simulation was realized through the thermal-structural coupling preload temperature differential method. The press model was established through Solidworks and ANSYS software was introduced. Half of the model was analyzed by finite element analysis, appropriate pre-tightening force was exerted, the pre-tightening forces on 30 degrees and 55.2 degrees were calculated using temperature differencial method and the pre-tightening effect was analyzed under limit load. The contrastive analysis results show that this method can well simulate the actual pre-tightening force.