In order to increase boronizing speed without decreasing the hardness of boride layer, the effect of plastic deformation at room temperature on powder RE-chrome-boronizing for a medium carbon steel (steel 45), in which boronizing plays a main role, was studied in this paper. The cold plastic deformation (CPD), whether compressing or shot-peening, can increase boronizing speed. Meanwhile, the boride layer can also retain its high microhardness (1 300―1 900HV0.1) with low brittleness. The layer depth achieved for a given heating time increases with increasing CPD degree on the steel. The analyses show that boronizing kinetics in the RE-chrome-boronizing (RE-Cr-B) samples with CPD can be enhanced.