To solve the problem of incomplete measurement and ill-posed in finite element model updating, a model updating method based on the Neumann series expansion of frequency response function (FRF) is proposed. First, the complete test FRF is calculated by modal data from test and finite element analysis. Then, equations between test FRF and analysis FRF are established according to Neumann series. In this way, the objective function of model updating is formulated. Finally, the modified whale optimization algorithm is applied to obtain the updating results. Numerical examples of a plane truss show that the proposed method is robust to noise and has good precision. With 15% noise, the average relative error after model updating is less than 1% . The method is further validated experimentally with the 4-story shear frame structure. Results show that the updated model can reflect the true status of the structure.