【Purposes】 Radiation therapy is an important method of personalized tumor treatment. Thermoplastic film is often used to fix the patient's position in clinical practice to ensure the repeatability and accuracy of treatment. 【Methods】 On the basis of CT images of a patient with head tumor, two different kinds of thermoplastic membrane finite element models were established. The material properties of thermoplastic film were measured by tensile experiments, and the displacement and stress responses of three thermoplastic film models with different thicknesses under load were simulated. 【Findings】 The results show that the displacement of the non-opening hole model is the largest, and that of the open hole model is the smallest. The stress of the model with full face opening is the highest, and that of the model without open face opening is the least. 【Conclusions】 This study provides research ideas and references for the study of thermoplastic film fixation effect and effectiveness, and also provides some reference for the personalized positioning therapy in the future.