Effects of shot-peening on Cr-Rare earth-boronizing at 650°C for 4 – 8h for medium carbon steel are investigated in this paper. The value difference in boron diffusion activation energy between shot-peening and undeformation is calculated. The layer depth, microhardness and brittleness are also analyzed. The results show that the activation energy has a decrease of 5647.78 J/mol after shot-peening for 1.5h, and the layer depth increases with prolonged shot-peening time. The layer can also retain its high hardness with low brittleness. The analysis indicates that shot-peening can provide a large number of crystal lattice defects that facilitates boron diffusion in the steel, and the low temperature is apt to remain high dislocation density.