With its large structure size（the outer diameter of inserted plate is 8.5 m）,narrow interval（595～620 ℃） of the post-welding heat treatment（PWHT）,and major difference of plate thickness（the thickness of dome head is 36 mm,the thickness of insert plate,penetration sleeve as well as flange are all 130 mm）,the PWHT process for equipment hatch is a big challenge. In this paper,the temperature uniformity of heat treatment furnace is measured to establish an effective heating area,which guarantees the precision range of heat treatment temperature. In this area,PWHT tests for module of dome head and flange and module of insert plate and penetration sleeves are carried out in furnace. The analysis results of tests procedure and heat treatment curves provide theoretical and data support for CAP1400 large penetration assembly PWHT.