On the basis of theory of dynamic modification and the finite element method, a numerical analysis modal of the response sensitivity of a mirror structure is established, and the influence of the random variables of the rotating mirror on the various order modals of the mirror is obtained. The structural size and material properties of the rotating mirror are used as random variables, and the rotating mirror feature value and feature vector are considered the response volumes. Results show that the radius R2 of axis segment 1 is the largest random variable that affects the first-order modal of the rotating mirror, the density D2 of the mirror body has the greatest influence on the first-order bending of the mirror, and the radius R3 of axis segment 2 has the greatest influence on the second-order bending of the mirror. The density of the spinning axis and mirror body are negatively correlated with each order modal, and R2 and R3 are positively correlated with the various order modals. Results provide theoretical guidance and basis for the selection of rotating mirror materials and the optimisation of the directional orientation of the dynamic parameters of a rotating mirror.