为了研究不同功率密度对激光冲击诱导的残余主应力及其方向的影响，采用5种不同功率密度对2024铝合金进行冲击，用X射线应力分析仪测量3个方向的残余应力，计算出残余主应力及其方向。结果表明，激光功率密度对冲击区域的残余主应力幅值、主应力方向角的分散程度、应力强度及最大切应力有影响；对于2024铝合金，功率密度为2.8 GW/cm2时，残余最大主应力的方差为1987，主应力方向角的方差为13905，残余应力分布均匀，主应力方向角分散，但残余最大主应力的均值为-158 MPa；功率密度为2.1 GW/cm2时，残余最大主应力的均值为-239 MPa，冲击区域的残余应力值最大，但残余最大主应力的方差为5471，残余应力分布均匀性差。

In order to study the effect of laser power density on principal stresses and their directions by laser shock processing (LSP). 2024 aluminum alloy samples are processed with five different laser power densities. Residual stresses of three directions are measured by X-ray diffraction (XRD), and the principal stresses and their directions are calculated. Experimental results show that effect of laser power density on the amplitude of principal stresses and the spread of its direction, stress intensity and maximum shear stress by LSP. The variance of maximum principal stress and its direction of 2024 aluminum alloy are 1987 and 13905 respectively, with the laser power density of 2.8 GW/cm2. Residual stress is of uniform distribution, and the angles of principal stress directions are scattered. But the average of maximum principal stress of 2024 aluminum alloy is -158 MPa. The average of maximum principal stress of 2024 aluminum alloy is -239 MPa with the laser power density of 2.1 GW/cm2. The variance of maximum principal stress and its directions of 2024 aluminum alloy is 5471. Residual stress is less uniformity.