In order to evaluate the jitter affection brought up by flywheel in optical satellite, this paper studies the principles in the jitter affection, promotes a theoretical analytical model and constructs a testbed with high fidelity. By studying the principles in the jitter affection, the transfer fuctions between input disturbances and output image motion are achieved, meanwhile, the harmonical and modal characteristics are proved theoretically. Secondly, a testbed with high fidelity is constructed to measure the real affected image motion. Finally, this paper compares the analytical data and test data and analyzes the reasons that brings in the differences. The results indicate that the harmonical characteristics in analytical data and test data coincide with each other well, the typical harmonic factors contained are almost the same. The modal characteristics are similar at low and medium frequencies within 8% error.