In order to study the failure characteristics of support and surrounding rock under the condition of mixed support, No.11002 Face of Zhaogu No.1 Coal Mine was taken as the background, the 3DEC numerical model was used to establish the combined mining model of bottom layer and coal pillar area. The research showed that after the top slicing mining, the deformation and failure of the mining surrounding rock mass near the coal pillars on both sides of the top slicing working face were more serious; When the bottom slicing mining entered the intersection area of the end section and the coal pillar area, the working face advanced to 84 m and 88 m. During the mining process of the working face, the support pressure should be prevented from rising due to the untimely roof collapse in this area. The research results provided a theoretical basis for the optimization of mixed support process and disaster prevention and control under complex geological conditions.