Abstract: In the fully mechanized coal caving mining face of Fenxi Xinyang Mine, the coal pillar left for the coal mining face was large.In order to reduce the coal pi Ilar width and improve the coal recovery rate of the coal mining face, base on the analysis method of the limit balance theory, the expression to calculate the coal pillar width was derived.With the relationship between the coal pillar strength and the high and wide ratio, the designed coal pillar width was as reduced from 35 m to 25 m.W ith the continued automatic sampling device, the actual measured data showed that the lateral support pressure scope of the coal pillar would be 1012 m. The coal width designed would be two times wider than the width of the plastic zone and the theoretical calculation and the measured results could be well fitted.The site monitoring an d measuring results showed that during the gateway driving period of the coal mining face, the gateway roof displacement at the coal pillar would be 85 mm, the conver gence between the two side walls would be 70 mm and the separation in the shallow section of the roof would be 8 mm and 10 mm individually.During the mining operat ion period, convergence of the roof and the two side walls was increased to 105 mm and 90 mm individually, the separation in the roof strata was not changed and the C oal pillar and the gateway could be kept in stable to meet the safety production requirements.