To improve the sensitivity of IR system, a research on reducing the vibrating noise of a multi !sensor IR seeker is given. Several kinds of noise that possibly affect the infrared signal are introduced, various causes that perhaps bring vibrating noise are analyzed,and the transfer function of the vibrating noise is constructed.A method is presented which can be used to reduce the vibrating noise by decreasing the vibrating amplitude or separating the vibration of missile from the seeker. According to the characteristics of the seeker,a kind of mathematical model of decreasing the vibrating amplitude is constructed and the differential coefficient equation of vibrating model of seeker is derived.The problem of vibrating noise of IR system is solved by using LAGRANGE dynamic equation and the method is applied in practice successfully.