Abstract: In order to determine the maximum plastic zone width of coal pillar under the action of self-weight of overlying coal rock mass near the goaf, the method of combining theoretical derivation, numerical simulation and on-site monitoring was adopted. By considering the arching effect of overlying coal rock mass in the goaf, the elastic-plastic analysis of coal pillar was carried out. According to the engineering conditions of Yuhua Coal Mine, the ANSYS simulation mining depth was 500 m and 600 m, the mining height was 4 m, 5 m, 6 m and 7 m, and the maximum plastic zone of coal pillar in the roadway of Yuhua 2410 working face was monitored. The results show that the results of theoretical calculation, numerical simulation and field monitoring of the maximum plastic zone width of coal pillar are consistent. The theoretical formula of the maximum plastic zone width of coal pillar in medium mining height is given, which can provide the basis for the design of coal pillar width.