Abstract: To reduce the phenomenon of inadhesion during the process of 3D printing, a method optimizing the print effect by reducing the compression degree was presented. The model of flexible shell was generated by Inventor and Cura, and it was produced using thermoplastic polyurethanes by 3D printing. The result of 3D printing did not accord with the anticipation, the inadhesion appeared on the surface of flexible shell, and the reason was explored in this study. Using different parameters to print the same shell, a result was confirmed that they are influencing the effect of 3D printing by changing the compression of height. For reducing the compression, some optimization methods were proposed, for example:adding supporting structure, turning on the radiator and setting the difference temperatures. Results show that all the methods have some influences on improving the print effect; however, adding supporting structure has more remarkable effect, and the inadhesion of 3D printing can be reduced from 8.2% to 2.5%. The optimization effect is verified.