Abstract: A calibration method of a large field LCOS splicing star simulator as well as the structure and principle of the calibration system were introduced. In order to make the star simulator to obtain a larger width of the field of view, proposing the connection technique of two LCOS was proposed. A variety of splicing errors were analyzed and then the calibration method was gave out. The focal length measurement error, distortion error and the imaging relationship error brought by the spliced LCOS were analyzed, a mathematical model of the angular distance between stars was established. Moreover, the various parameters of the model under the optimal accuracy were calculated by using a large number of the measurement data. Experimental result shows that, after calibration, the accuracy of angular distance between stars from the star simulator is significantly improved and the measurement error is better than 20.