Film casting is an important forming technological method for the manufacturing of single or multi-layer films for the electronics, medical and packing products. In polymer film casting process, the processing conditions can significantly influence the performance and dimension of final products. However, proper control of practical processing conditions is still a difficult task. In the study, the mathematical model of three-dimensional film casting process is established using a membrane model. The corresponding finite element formulations is derived based on standard Galerkin method and the details of numerical schemes are introduced. The essential flow characteristics and the variation of film parameters in polypropylene film casting process are investigated based on the proposed mathematical model and numerical methods, which show good agreement with corresponding experimental observations. The evolutions of neck-in and edge bead phenomena are successfully predicted and the influences of processing conditions as draw ratio and air gap length are further discussed