Conditions of open-pit and underground united mining,The open-pit slope is located in the underground mining affected area,two types of mining effect interaction, overlap and interact with each other,thus constitute a composite superimposed effect,The slope rock mass performance for superimposed deformation mechanism of the open-pit mining and the mining effect.This paper takes an ex-ample of Zijin mountain gold-copper mine open-pit and underground united mining.Midas-GTS software is used to establish the 3D model of the side slope body of Open-pit and underground united mining, and the numerical analysis is carried out by using FLAC3D software.The horizontal displacement,the sinking value and the stress value of the rock mass are studied.The deformation mechanism of the slope under the condition of open-pit and underground united mining is summarized.