The 42CrMo was treated by grinding hardening and making induction hardening test and the micro-structure, hardness and thickness of the two strengthened layers were compared and studied. The results show that the thickness of enhanced induction strengthened layer is uniformity, the structure of strengthened layer and microhardness of it’s cross section are homogeneous, the martensite organization is fine needle-like; And the thickness of grind-hardening strengthened layer is uneven, the main martensite organization of strengthened layer is lath-like, and the change rule of the organization is from fine to slightly coarse, then to fine. The change of microhardness is obvious in strengthened layer.