The stability of slope is a combination of external factors.By the local deformation extended and evolved into the overall destruction of disaster process eventually.In the process，the factors of controlling the deformation of slope is “dynamic”.The multistage slope of not supported is excavated.The stability and deformation of slope are analyzed under different steps.The slope is supported according to the results of the calculation.The stability and deformation of slope are analyzed under supported.The comparison results show.If the slope is supported in timely.The safety factor of slope is reduced in the early excavation.But it will increase in the late.The monitoring points of horizontal displacement and vertical displacement of the slope both reduce after supported.