It’s necessary to research and analyze the correctness of internal stress measurement, in order to effectively deal with the measurement problem of stress field and rightly describe the distribution character of stress in aluminum alloy thick plate. Firstly, the total uncertainty of stress calculation in layer removal method (LRM) is determined by experimental error and model error, and less than ±10MPa, in which the accuracy of experiment is high. Secondly, in the integral calculation of LRM, a modified function is proposed by the multi-methods of simulation and experiment, and can compensate the deviation resulted from unpredictable error for experimental conditions. Then the multi-methods achieve the value of X-ray surface stress, simulation calculation and experimental results to consistent, the correctness of experimental calculation is enhanced. The research presents that the LRM can exactly describe distribution of internal stress in thick plate under special experiment conditions.