Abstract: Heat treatment of different isothermal holding time was carried out on 50Si₂Mn₃ cast steel at temperatures around A₁ point in the strong magnetic field of 12 T, and the influences of magnetic field on the amount and the morphology of transformed pearlite were investigated. The results show that at a high temperature below A₁ point, high magnetic field of 12 T could shorten the incubation time for pearlite to transform. In other words, magnetic field could promote pearlite transformation, increasing the amount of transformed pearlite. Magnetic field of 12 T could raise the critical temperature of pearlite transformation, making the transformation of pearlite at above A₁ point possible.