Abstract: Segregation defects are prone to appeared in the core of 2Cr12NiMo1W1V stainless steel for steam turbine blade, which affects the qualified rate of products. The causes of segregation defects were studied and analyzed by experiment. The results show that the segregation defects in the tested steel was due to the slow cooling rate in the solidification process after refining and the slow solidification rate in the molten pool during electroslag remelting. After improving the smelting process, both the casting temperature and the electroslag remelting speed of the tested steel were reduced, the segregation defects could be improved effectively.