The working condition of aqueduct can be analyzed effectively by mathematical monitoring model based on measured data. The reliability of measured steel bar stress, however, is difficult to be confirmed as the mathematical model is prone to be affected by the experience and multicolinearity due to the complex working conditions of aqueduct. In this research, the statistical model and mixed model of measured steel bar stress of a large aqueduct were established based on measured data; subsequently, the parameters of the established models were estimated using stepwise regression and compound model method to compare the water pressure components separated by different models. The analysis result showed that although the measured stress of steel bar No. 2 in the aqueduct is somewhat regular, the variation law of the water pressure component separated by different analysis methods does not conform to the general laws of mechanics. Therefore, the measured value of the steel bar is considered abnormal and unreliable, hence cannot be employed to analyze the actual status of aqueduct.