Aiming at the problem that the existing accuracy evaluation methods can not effectively calculate the accuracy of star sensor under large dynamic conditions, a dynamic accuracy evaluation method was proposed based on the imaging model of star sensor and the invariance of star angle distance. The principle was clarified, and the calculation flow and statistical method were proposed. Based on the in-orbit data of FY satellite, the processing results of the proposed method and the traditional sliding window method were compared and the equivalence of the two methods under the same condition of small angular rate was analyzed, which verifying the feasibility of the proposed method. Based on the ground observation data, the measurement accuracy of two types of star sensors under different dynamic conditions was obtained. Compared with the existing dynamic accuracy evaluation methods, this method can effectively peel off the errors introduced by the test system, and more truly reflect the actual measurement accuracy of the star sensor under dynamic conditions.