In order to measure the coaxiality error of GNSS antenna connector, a mathematical model of segment rotation of connector is constructed, and a non-contact measurement method combining horizontal turntable and machine vision is proposed. Then the measuring device is built and the measuring experiment is carried out. Based on the analysis of the motion mode of the connector and the measurement method of coaxiality error, the deviation relationship between the axes is determined, and the mathematical model and measurement model of coaxiality error are established. In the measuring device, the camera is mounted above the horizontal turntable with the optical axis parallel to the horizontal turntable axis. Rotate the horizontal turntable, use the camera to capture the center position of the end face of the transfer screw and fit the orbit, and complete the self calibration of the coaxiality error of the measuring device. Place the connector on the horizontal turntable, rotate the horizontal turntable, and measure the deviation of the thread axis at the top of the connector from the axis of the horizontal turntable. Rotate the carrier of the connector, and measure the deviation of the thread axis at the top of the connector from the axis of the carrier. Finally, the maximum coaxiality error of the connector is obtained by synthesizing the deviation relations of the axes. The standard deviation of measurement device for coaxiality error of GNSS antenna connector is 9 μm, and the expanded uncertainty of single measurement result is U=30 μm (k=2), which meets the measurement demand of coaxiality error of GNSS antenna connector in the level of 0.1mm to 1mm. Using connector coaxiality error to correct GNSS ultra short baseline measurement results can significantly improve the baseline measurement accuracy.