Due to the processing and manufacturing uncertainty the actual structure system often has a lot of uncertainty. How to accurately assess the dynamic behavior of the uncertain system, it not only has the practical significance, but also is a research focus on the structural theory in recent years. In this paper the dynamic behavior of the structure with uncertain parameters under external random excitation is investigated. The uncertain parameters of the structure are modeled by the random variable, and the random excitations are modeled by the stochastic process. The hybrid Polynomial Chaos and Pseudo Excitation Method (PC-PEM) are proposed to evaluate the random vibration response of the uncertain structure. Finally, the proposed method is applied to evaluate the random response of a 21 bars truss with uncertain parameters. The first two statistical moments are discussed, and the correctness and effectiveness of the proposed method are verified compare with the Monte Carlo Method. This work is of great significance to the random vibration analysis for the complex equipments and structures with the uncertain parameters.