Abstract: Effect of heat treatment parameters such as austenitizing temperature, holding time and isothermal temperature on the carbide spheroidizing for steel T12 is studied by using orthogonal test method in this paper.The results indicated that austenitizing temperature was the most important factor, which affected carbide spheroidizing for steel T12, the holding time and isothermal temperature were the secondary ones, and the better heat treatment process for steel T12 was austenitizing at 755 ℃ for 1 min and then annealing at 690 ℃.The specimen prepared with the better heat treatment process had the spherical pearlite of small uniform carbide.