[Background] The soil disintegrating characteristics is an important indicator of the soil erosion of red soil in southern China, and also the critical basis for conducting the soil conservation. Tongcheng county is one of the typical granite regions in southeastern Hubei Province, with the largest quantity and the most centralized distribution of collapsing gullies. Samples selected in Tongcheng are representative in the subject. [Methods] The influences of the correlations between the initial soil moisture content and the disintegrating characteristics of different soil layers on the occurrence mechanism of the collapsing gullies were analyzed. Soil samples of two 3-meter-TVD (true vertical depth) soil profiles were collected in Tongcheng. According to different criteria such as color and texture of weathering crust of granite, the soil profiles can be divided into 4 different layers from top to bottom,including the eluvial horizon, illuvial horizon, transitional horizon, and parent horizon. To each horizon, this study set 6 experimental groups of 6 different levels of initial soil moisture from dry to saturation, by controlling the length of air-drying duration, and using disintegration tester to conduct disintegrate experiment with the soil samples. [Results] The results proved that at different levels of the initial soil moisture content, soil of eluvial horizon and illuvial horizon disintegrated in a slow progress and the soil of transitional horizon and parent horizon did fast. The initial soil moisture content had a considerable effect on the speed to complete the disintegration of the eluvial horizon and illuvial horizon, while little impact on the easily-disintegrated soil of the other two layers. The maximum disintegration also was affected by the initial soil moisture content, the maximum disintegration of the eluvial and illuvial horizon significantly increased with the decrease of the initial moisture content, and the disintegration was approximately complete under air-dried condition. The disintegration of the transitional and parent horizon was fully completed at any level of initial soil moisture content, so the maximum disintegration was less affected by the initial soil moisture content. Drawing and analyzing the graphical sheets of the disintegration amount of different horizons in different soil moisture, the graphs showed that the disintegration amount presented an increasing trend with the time varying; the influence of disintegrating time on the disintegration amount of the transitional and parent horizon at different levels of initial soil moisture content appeared S curve. [Conclusions] Hence, it can be inferred that in a granite profile, the soil of the transitional horizon and parent horizon disintegrated more easily and formed the niche, which resulted in the head erosion of the collapsing gully. This provided a basis for further research on the collapsing of granite and laid a foundation for the study of the occurrence mechanism of the collapsing gullies.