Eigenvalue sensitivity analysis model of rotating mirror has been established by means of numerical analysis based on the theory of dynamic modification. The loop files of eigenvalue sensitivity were got based on the modal analysis. With the Latin hypercube sampling of Monte Carlo, the data of structure parameters were sampled by the probability density of the structure size of rotating mirror. The Spearman rank correlation coefficient between eigenvalue and structure size was obtained by calculation. The result shows that the spearman rank correlation coefficient of basic variables is different from each other, which reveals that the variables impact the natural frequency in different ways. According to the result, the circumcircle radius of the mirror body was modified, the numerical analysis and experiments of the two rotating mirror were done. The results show that the first-order modal rotating mirror is increased 101.8%, the first critical speed is 8.7 105 r/m and the dynamic performance of rotating mirror is effectively changed. This indicates that the way of eigenvalue sensitivity analysis based on the results of numerical analysis to optimize the structure size of the rotating mirror is a practical and effective method.