Abstract: The CCT curve of 00Cr25Ni7Mo4N super duplex stainless steel was obtained by thermal dilatometry, and the influence of cooling rate on precipitated sigma phase was studied by combining with metallographic observation, micro hardness measurement and XRD. The results show that the temperature of heat treatment and hot working should be controlled above 1050 ℃. The less the cooling rate, the more the content of precipitated sigma phase, and the higher the micro hardness. The cooling rate over 4800 ℃/h in the range of 600-1000 ℃ should be ensured to avoid the hot brittle sigma phase.