Abstract: The safety and durability of the soil slope can be threatened when the strength of soil is deteriorated due to wetting-drying cycles. Experimental studies are undertaken on an undisturbed residual soil from southeast of Fujian area. It aims to discuss the variation of shear strength with the change of water contain and the cyclic number under wetting-drying cycles. It is shown that the cohesion of granite residual soil decreases in different degrees with increasing number of cycles and finally reaches to a constant state. However, the friction angle of granite residual soil keeps a stable with little influence of the wetting-drying effects. On the basis of the relationship between the amount of strength attenuation and cyclic number, the S-shaped function is adopted for fitting. The results show that the S-shaped function can well describe the attenuation rules of cohesion with the change of cyclic number. The results also have an important reference value for further reveal the influence of wetting-drying cycles on deterioration mechanism of granitic residual soil and long-term stability of residual soil slope in southeast of Fujian.