Regarding the problem of seasonal and shallow sliding when the slope of the navigation channel is swelling soil，which affects the shipping capacity and engineering safety，we carry out the straight shear test of swelling soil after reciprocal wet and dry cycles and the stability analysis considering the effect of wet and dry cycles based on the treatment project for the destabilized slope of Nanjing section of the Wu-Shen Navigation Channel. The results show that the cohesion and internal friction angle of swelling soil decay gradually with the increase of the number of wet and dry cycles，and the decay mainly occurs in the first three dry and wet cycles，and then gradually stabilizes. The decay degree of cohesion is much larger than that of internal friction angle. Considering the soil strength decay caused by the wet and dry cycle effect is the correct calculation method to obtain the true stability coefficient of swelling soil slopes. The treatment measure of using gate-shaped anti-slip piles is proposed for the unstable slope，and has good application effect and engineering reference significance.