Stress inspection of large diameter circular saw can be accomplished by the deformation measurement, and the result will fluctuate because of the vibration of the saw in the detection process. In order to improve the accuracy of measurement, a detecting algorithm was presented based on curve fitting. The fixed size sliding window method was used to reconstruct the quantitative data, and a new data structure was formed. The detection noise can be decreased by curve fitting of the data structure. The deformation inspection system was developed and a 1 700 mm diameter sample was measured. Results indicate that the proposed algorithm reduces the deformation errors brought by detection system itself and vibration of circular saw blade. The measurement precision is up to 0.02 mm.