Abstract: A reasonable size coal pillar can not only ensure the stability of the roadway, but also increase the recovery rate of coal.Taking Tongchuan Yuhua Coal Mine as the background, the reasonable leaving width of the section coal pillars is determined by the method of combining stress dynamic monitoring, theoretical derivation and engineering verification.Stress monitoring on the 2410 working face found that compared with the coal pillars on the side of the goaf, solid coal has a higher bearing capacity and a larger stress increase.Under the influence of mining, the peak stress transfer time to the deep part is later.In order to further determine the specific width of the coal pillars, considering the arching effect of coal and rock mass collapse after mining at the working face, a force-transmitting arch model of the overlying rock mass transferring load to the coal pillars is established, and the distribution law of the supporting pressure of the coal pillars is studied.After clarifying the load transfer mechanism and the force of the coal pillar, combining the limit equilibrium theory and the rigid plastic theory, the reasonable leaving width of the coal pillar between the fully mechanized mining face and the reinforcement range of the coal bank are obtained.According to the research results, the engineering verification is carried out, and the observation results of the roadway surface displacement show that the designed coal pillar size is reasonable and reliable.The research results have reference significance for the determination of the section coal pillar width under similar mining conditions.