Abstract: The value and direction of static friction are various with the external force. Based on the Euler’s friction law, the internal force in a flexible belt surrounded in a fixed cylinder is exponential distribution when it is in critical status, or just before macroscopic slipping. In this paper, the internal force distribution and relation between force and deformation of the belt was studied when the external force loaded and unloaded. The results show that internal force can be increase or decrease in exponent at any point of the belt, which is determined by the loading history; although the belt is linear elastic material, the relation between external force and the total deformation is nonlinear. The relation in unloading process is different to the loading, and a hysteretic loop is produced in the curve of force and deformation. And every point inside the loop is a capable state of the force and deformation of the belt.