The workpiece table is one of the most core technical units in the TFT array substrate long-inch measurement equipment， and its positioning accuracy would directly determine the final measurement accuracy. During the movement of the workpiece table， it would produce movement errors due to the processing and assembly errors of the moving guide rail， which could affect the measurement accuracy of the TFT array substrate. In order to solve the above-mentioned influence of the movement error of the workpiece table， the mechanism of the influence of workpiece table movement error on the measurement accuracy of long inches was analyzed based on the bridge structure of the long measuring equipment， and a common optical path with multiple degrees of freedom was designed. The laser interferometer measurement system could provide the beam structure layout and measurement compensation scheme of the laser interferometer measurement system. By building a test platform， the repeatability before and after compensation of the motion error of the workpiece stage and the repeatability of the final long-inch measurement were tested based on the 4.5-generation substrate. The test results show that the workpiece table movement error measurement and the compensation technology studied above could meet the technical requirements of 100 nm high-precision positioning accuracy of the movement table.