Some problems such as large number of grids, high calculation cost, large proportion of memory and slow calculation efficiency may be encountered when calculating the dynamic characteristics of full-scale aircraft structures.In order to exclude the redundant local mode from the frequency range of interest and emphasize the main overall mode,the method of increasing the out-of-plane stiffness of the shell element is proposed. The accuracy and efficiency of the method are verified by using a box model and a full-scale aircraft model.The simulation results show that, the calculation efficiency of full-scale aircraft structure is increased by more than 100 times. As a result, the file storage space is reduced by nearly 10 times. The maximum error of the first 6-order modal frequency of full-scale aircraft is only around 4%.