In order to investigate the influence of morphological characteristics of upper jaw of crocodile on its structural features and apply obtained results to bionic design, it is necessary to extract and analyze the upper jaw surface of crocodile. Reverse engineering technology was used to perform the 3D reconstruction for crocodile skull. In combination with the polynomial fitting method, the mathematical models for three surfaces, which were divided according to biological morphology, were established, respectively. The data of three mathematical models were merged and compared with the biological model for deviation. The results show that the determined coefficient values of fitting equations for three mathematical models are all close to 1 after fitting with the standard deviation of acceptable variation range. The complex biological surface model can be transformed into multiple mathematical models, and the data of multiple mathematical models can be merged into a complete model, which can provide a basis for the research of mechanical properties of crocodile skull and bionic engineering design.