In tropical rainforest area, the climatic is characterized by heavy and concentrated rainfall, the lithological is characterized by strong weathering and large weathering depth. In this study. According to the K110+410 fully weathered rock slope of Xiaomo expressway, the engineering geological method was used to determine geologic model of landslide surface that is located at the unconformity contact surface caused by the difference of permeability of the upper and lower strong weathered rock layers. The finite element strength reduction method was used to simulate the excavation process of the slope, and the strain incremental cloud map was analyzed to reveal the deformation and failure mechanism of slope; excavation is the main factor of slope instability, rainfall intensifies deformation and failure of slope. Comparing to the passive reinforcement, active reinforcement has the following advantages, such as high design parameters, controllable deformation, small environmental disturbance, and small quantity of reinforcement. The reliability of combined reinforcement of and anti-slide pile and bolt is certified by two rainy seasons monitoring of the reinforced slope. The results can provide technical support for reinforcement of full-strength weathering slope in the tropical rain forest.