Before the production of products,it is the mainstream mode of equipment research and development to use the digital design or simulation technologies to comprehensively evaluate and optimize their performance. As complex structures,it is inevitable that there are some differences between the simulation model and the real model due to the simplification of model and other reasons. In this condition,Model confidence is an important factor to evaluate whether a simulation model can effectively guide the structural design. The paper analyzed the equivalent modeling method of dynamics model of complex structure and the influence factors in the simulation model. A bottom-up model updating method was proposed which is combined with the characteristics of electronic equipment structure. A typical case was given to verify the feasibility of the method. The simulation model satisfying the requirement of engineering precision is obtained by using the bottom-up model updating strategy,which lays a foundation for the subsequent design and simulation of similar products.