The dispersed fringe co-phasing error detection technology needs a certain method to analyze and process the acquired dispersed fringe image to obtain the corresponding piston error value. Compared with other dispersed fringe image processing methods, the main peak position extraction method can be applied to the detection of piston error in large range or in small range within one wavelength. However, the detection accuracy of the method is very sensitive to the calibration error in the central line position of the dispersed fringe. To modify the effect of this calibration error, this paper firstly proposes a self-adaptive extraction method for fringe central line position based on the analysis of the influence of the piston error on the diffraction pattern of double rectangle hole. Based on this, combined with the basic principle of the main peak position extraction method, a method of correcting the influence of fringe central line calibration error is proposed. Finally, an experimental light path is built to verify the effectiveness of the proposed correction method. The experimental results show that the proposed method can achieve a measurement accuracy of less than 30 nm in the presence of the central line calibration error, which is greatly improved compared to the accuracy before correction. This method effectively improves the anti-jamming capability and engineering practicality of the main peak position extraction method.