Based on issues like instability of collapsing gully wall caused by the development of granite exposed areas which vulnerable to the impact of wet and dry cycles, by a series of unconfined compressive strength test, we determined variation patterns of the unconfined compression strength under wet and dry cycle at different layer soils in collapsing gully, and established a predictable model of unconfined compressive strength combined of soil depth ratio and dry wet cycles at different levels of soil collapse. The results showed that: The unconfined compression strength at surface soil layer, red soil layer, speckle layer, detritus layer decreased most after 1st wet and dry cycle, of 26%, 15%, 40% and 49%, respectively; the decrease slowed down after the 2nd to the 4th wet and dry cycle; the unconfined compression strength remained stable after the 5th wet and dry cycle; with the increase of wet and dry cycles, the unconfined compression strength of dilapidated granite at different soil level generally performed as surface soil layer＞red soil layer＞speckle layer＞detritus layer; under different wet and dry cycle times, the stress-strain relationship curve tended to soften and reached the peak at 2% strain, but at red soil layer, the fluctuation tended to be intense after the 3rd wet and dry cycle; the predicted value of the unconfined compression strength correlated with measured value significantly (R2=0.91), the model had certain value forecasting wet and dry cycles on unconfined compressive strength of different layer soils in collapsing gully in Tongcheng areas.