Abstract: The change of soil mechanical parameters of seasonal frozen soil under freezing and thawing cycles in Changchun area is studied. Soil samples were taken from typical soil layers and tested in the laboratory. The physical and mechanical parameters of soil samples under three different conditions, namely undisturbed soil, primary frost-thaw soil and secondary frozen-thaw soil, had been tested, compared and analyzed.The variation law of mechanical parameters under the action of the second frozen-thaw cycle were concluded. The frost heave and thaw settlement under the action of the second frozen-thaw cycle were also tested, and the main factors affecting the frost heave of foundation soil were analyzed in detail. The corresponding prevention and control measures were put forward according to the influencing factors.