Dynamic stiffness is a parameter of the system structure to resist external dynamic excitation. By analyzing and optimizing the dynamic stiffness of key points of the body, the performance and comfort of the vehicle NVH can be effectively improved. To a certain type of car body as the research object, this paper introduces the basic concept of dynamic stiffness and related theory, and in view of the body has the problem of excessive vibration, using HyperWorks software to establish finite element model of the white body, the key points to select 15 body vibration frequency response analysis and dynamic stiffness analysis, find the dynamic stiffness of relatively weak point and frequency band. Taking the problem of insufficient dynamic stiffness of engine suspension left connection as an example, local topology optimization and modification scheme are carried out to improve the NVH performance and ride comfort of the vehicle.