Abstract: In order to improve the reliability of measuring results of welding residual stress, it is needed to analyze the error factors in the process of the residual stress measured by hole drilling method. The error expression where strain error and release coefficient error are passed to the final measuring result has been derived according to the theory of error propagation and one error chain that affects the accuracy of final measurement result is established by the influencing factors of actual measurement error. Taking 2A12 high strength aluminum alloy plates after VPPA-MIG hybrid welding into measuring experiment, the relative error of final measuring that results from the error of elastic modulus, the error of strain gauge paste and the time error of strain reading in the error chain are quantitatively analyzed. The relative error of residual stresses σ₁ and σ₂ from the error of elastic modulus are both very small. The relative error of residual stresses σ₁, σ₂ and ? angle from the error of strain gauge paste all reduce to 0% after the strain patch is pasted for 24 hours. The relative error of residual stresses σ₁, σ₂ and ? angle from the time error of strain reading all reduce to 0% after 150 minutes of strain release.