For an active vibration control system based on Filtered x-LMS algorithm, the modeling of secondary path affects stability and effectiveness of the controller. Traditional secondary path identifying methods either online or offline way need to be carried out after the whole active control system is constructed and installed. In general, it will cost a lot to obtain the secondary path model in a practical engineering case, since the active control system will be bulky especially for a multi-input and multi-output system. In this paper, a pre-identifying method of secondary path is proposed which includes three steps. Firstly, the transfer function concerning the actuator and its related equipment is modelled in the laboratory in advance. Then, the dynamic behaviors of secondary path concerning physical structure being controlled is identifying by the impact method. At last, the model of whole secondary path is obtained by convolving the results from the previous steps. A comparison between the pre-identifying model and the traditional one using LMS algorithm shows that the proposed method is feasible.