In order to study the effect of laser shock processing (LSP) on valve spring based on shot peening (SP) and heat setting, the valve spring manufactured by different processes were treated by LSP with high power Nd∶YAG laser. The effects of valve spring on mechanical properties after LSP were analyzed from residual stress, micro-hardness and microstructure. The results indicate that the effect on valve spring after LSP is similar to that after SP. The strengthening effect of valve spring by LSP based on SP is obvious. After LSP, the residual stress of valve spring based on shot peening twice reaches maximum value -541MPa and the micro-hardness of valve spring surface based on shot peening twice and heat setting reaches maximum value 668.4 HV. The variation of micro-hardness on valve spring surfaces manufactured by different processes after LSP is mostly identical to that before LSP. The grain refinement occurs after LSP and the primary cause of improving micro-hardness is grain size and strengthening phase.