Abstract: In order to solve the problem that the stress of coal pillar is different with time and space position, and the distribution characteristics and laws are not clear in the current open-pit coal mining technology, this paper takes an open-pit coal mine as a case study, and uses FLAC3D numerical simulation method to analyze the dynamic stress distribution of single side coal wall and supporting coal pillar, the stress distribution characteristics of coal pillar in the section and the stress of permanent coal pillar distribution characteristics, get the relevant laws. The results show that: the single side coal wall is in the area of increasing lateral supporting pressure of the working face; the stress concentration appears in front of the supporting coal pillar, and the stress distribution presents the "Hump" type; after the end of the section mining, the stress of the coal pillar in the section increases with the mining depth, and the stress decreases gradually; the stress distribution of the permanent coal pillar presents the "peak" type in the mining process, and there is an elastic core in the middle of the coal pillar district.