Abstract: The surface decarburized behaviour of Si-bearing medium carbon steel and the effect of C and Si on the decarbonization have been investgated through three kinds of heating and rolling process. By using metallograph analysis method to observe the surface decarburized layer structure and measuring the microhardness from the outside to the inside of the samples,it was found that adopting the method of heating and rolling in the protective reducing atmosphere is the best process to prevent Si-bearing medium carbon steel from surface decarbonization,and the carbon concentration in the atomsphere should be about 15 times of the sum of the C and Si contents in the steel.