This paper presents the development and validation of an auto-modeling technology for generating the finite element models of multi-bolt composite joints. Firstly, a highly efficient modeling strategy for bolted joints are introduced, the shell elements are used to model the connected plates, the bolts are represented by a combination of beam elements coupled to a serials of additional contact nodes, the contact between bolts and plates is simulated by Gap elements for NASTRAN. Secondly, the procedure of the auto-modeling technology is explained and the corresponding code is programed with PCL (Patran Command Language) to implement the models generating, which can read modeling control parameters in the data files and generate the finite element models automatically. Thirdly, the auto-modeling procedure is discussed in detail, including the meshing method for both single bolt joint and multi-bolt joint. Finally, a structural optimization based on the auto-modeling technique and an optimization program of GA (Genetic Algorithms) is carried out, and the result shows that the auto-modeling technique proposed in this paper is highly efficient and time-saving, and its application will help to shield engineers from the complex and time-consuming model creation process.