Due to the perennial freezing and thawing cycles，the soil structure in plateau mountainous area dete? riorates continuously，which adversely affects the pile-soil interface and the stability of structures. In this paper，the indoor laboratory tests and numerical simulation were carried out，a freezing-thawing cycle degradation model of soil structure was established，a coupled mathematical model of water-thermal-mechanics considering soil structure deg? radation was then established，and its reliability was also verified. Based on this，the stability of pile-soil system in plateau mountainous area during service period was numerically analyzed. The experimental results show that the soil permeability coefficient and pore ratio increase logarithmically with the number of freezing-thawing cycles，the soil cohesion decreases exponentially with the number of freezing-thawing cycles，and the internal friction angle in? creases logarithmically with the number of freezing-thawing cycles. During service period，the maximum frost heave displacement around soil gradually decreases with the increase of service life，and the maximum thaw settlement dis? placement also decreases. As a whole，the around soil shows a thaw settlement trend. The frost heave displacement of pile decreases gradually with time，the thaw settlement displacement increases as well，and the growth rate of frost heave and thaw settlement continuously decreases. However，the thaw settlement displacement of pile is larger than its frost heave displacement. Test results can supply some technical support and theoretical guidance for the design of pile foundation in plateau mountainous areas.