For chamber pressure tester for environment factor of the calibration data processing using the least square method for linear fitting, ignore the influence of abnormal value problem, the author uses the minimum distance square method and the weighted least squares method respectively to fit the calibration data of the two methods, from F significance test and sample analysis of simulation results of determination coefficient two aspects, and with the least squares method, To find a convenient method for fitting the data collected in the harsh environment of high temperature, high pressure and high impact to replace the least square method, so as to obtain the sensitivity coefficient with high confidence, which can provide data basis for the design of weapon barrel. The simulation results show that the minimum distance sum of squares method has the best fitting effect, but its accuracy is very small compared with the least square method. Considering the least square method is more suitable for linear fitting of the calibration data of chamber pressure because of its simple use.