The elastic elements manufactured by different treatment processes were treated by laser shock processing (LSP) with high power Nd:YAG laser. Residual stresses on inner surface were measured by X-ray diffraction (XRD) and principal stresses were calculated. The relationship between residual stress and residual principal stress was analyzed, and the influence of LSP on the elastic element fatigue source was discussed. The results indicate that residual compressive stresses on surface of springs were obtained. The quantitative relation exists between principal stress and residual stress. To prevent the crack expansion, the direction of residual maximum principal stress was changed and the residual stress at 0° was controlled.