[Background] Collapsing hill is a serious soil erosion phenomenon in granite areas of south China, it causes severe damages to ecological condition, agriculture and economy. The decrease of soil stability usually contributes to the collapsing hills. Soil shear strength is an important indicator to investigate the stability of collapsing hills, soil moisture is also the key factor of shear strength and the critical basis for conducting the soil erosion. [Methods] This study used a direct shear test to analyze the relationship and regularity of shear strength variation with soil moisture in different soil layers.According to the variation of soil characteristics such as color and texture, soil profiles can be divided into 4 layers, including the eluvial horizon(A), illuvial horizon(B), transitional horizon(BC), and parent horizon(C). The undisturbed soil samples were collected from two collapsing hills in Tongcheng County,southeast of Hubei Province, where is one of typical granite collapsing hill regions in China. To each horizon, there were 5 soil moistures from dry to saturation by controlling the length of air-drying duration.After pre-treatment, the samples were tested for different normal pressure (50, 100, 150, and 200 kPa)and various soil moisture. All of the tests were repeated once. Excel 2010 and SPSS 22.0 were used to analyze the relationship and Pearson orrelation of shear strength and soil moisture. [Results] With the increase of soil moisture, the shear strength of layer A increased first and then decreased, others showed a trend of descent in soil shear strength, the shear strength reached the maximum in layer B and minimum in layer C. Besides, soil moisture affected the shear strength of layer B most, the shear strength of layer BC was among all the layers. Soil cohesive force presented wide variations, layer A showed a trend of decrease after first increase, the cohesive force of remaining soil layers declined with the increase of soil moisture; the cohesive force of layer B was the largest among four soil layers, while its decay amplitude was large as well; due to the lack of clay content and cementing substance the cohesive force of layer C was very low. The internal friction angle decreased with the increase of soil moisture in all of the soil layers. [Conclusions] Therefore, the shear strength of granite profiles decreases with the increase of moisture generally from top to bottom, the bottom layers of granite are fragile and more likely to be eroded, which can accelerate the formation and aggravation of collapsing hills, protecting the bottom layers is vital to prevent the aggravation of collapsing hills. This study can provide a theoretical basis for mechanism research of slope collapse and erosion hills as well as contrcol works.