Aiming at problems such as complicated calibration models and trivial test progress, which are occurred during the calibration of installation error for star sensors, a novel ground calibration method of installation error based on three positions was introduced. Firstly, a mathematical model of installation error was established according to Euler transformation of coordinate systems. Secondly, a new ground calibration strategy of installation error based on three typically-selected positions on a triaxial precise turntable was put forward. The least square method and three positions method were adopted to conduct simulation contrast experiments. Simulation results demonstrate that calibration result stability of three positions method increases by nearly 10 times than calibration result stability of least square method. Furthermore, three positions method has simplified the calibration test procedure, which has important practical reference value to improve the operational accuracy of star sensor.