Abstract: A simulation system is developed to investigate the change in skin friction of piles due to the loading and unloading on the surface of soil. The system consists of four subsystems: loading and unloading, model piles, measuring system and automatic data acquisition system. The system can get higher pressure with the help of the pneumatic loading method so as to simulate the impact of soil compression and rebound on model piles under different soil properties and end restraint conditions. The validity of the apparatus is verified by elementary tests. The test results show that the system with high intelligence can achieve long-term constant load. Different end restraint conditions of piles are observed to have a significant influence on distribution of skin friction along the pile. And the strong rebound of the soil has little effect on skin friction of the upper part for bottom fixed piles and the whole for bottom free piles when the unloading ratio reaches 0.8. The system can be used to simulate the effect of the soil loading and unloading on piles.