In recent years,portal anti-slide pile has been widely used in the treatment of large-scale landslide geological disasters because of its high energy efficiency ratio and more economical and effective reinforcement.The selection of design parameters of portal anti-slide pile is a difficulty in practical engineering,so this paper uses the method of numerical simulation to optimize the selection of design parameters.Firstly,the reinforcement mechanism of portal anti-slide pile is expounded,and the coupling effect of pile and soil is analyzed in detail.Then,based on the change of slope stability after reinforcement and the morphological evolution of potential slip surface,the design parameters of pile are optimized and analyzed.On this basis,considering that the remarkable feature of portal anti- slide pile is the force coordination of pile structure under the action of tie beam,this paper focuses on the quantitative analysis of the force coordination of portal anti-slide pile structure under graded surcharge.What's different is the load sharing ratio is used to quantitatively analyze the stress coordination of front and rear rows of piles,and studies its variation law under different design parameters.The optimum pile spacing and pile row spacing are 3D~ 5D and 3D~ 4D respectively (D is the pile diameter).Finally,the exponential function equation of the relationship between pile top displacement and surcharge load under the condition of optimal pile design parameters is established. This study will provide a theoretical basis for the design and deformation control of portal anti-slide pile.