The accuracy of position sensitive detector(PSD) is mainly affected by the non-linearity, interference and the installation tilt error, and the measurable range is limited by the size of the detector. Based on the analysis of the influencing mechanism of the non-linearity, the interference and the installation tilt error, a speckle tracking system was introduced to remove the influence by local fitting and real-time calibration according to the linear relationship between the actual value and the measured value. Al2O3/PEN sample was used to experimentally verify the designed spot tracking system platform. The results show that the linear correlation coefficient maintains in a range of 1±0.001 5, the linearity standard error is reduced to 0.3 μm/40 mm, the maximum error is less than 16 μm/40 mm and the measurable range can be increased to the stroke of the module, 200 mm in this work. This method is effective, flexible and practical for position detection applications especially under feeble light condition and for large measuring range.