Abstract: In order to explore the pore size structure of the coal measures limestone reservoir, a pressurized mercury test was conducted in Limestone K2 of Taiyuan Formation near Fault F7 of Yitang Coalfield. In combination with the fractal model, a quantitative analysis was conducted on the heterogeneity of the pore size structure and the mutual relationship between the fractal dimension and the pore size structure parameters. A comparison was conducted with the fractal features of other reservoirs. A discussion was conducted on the hydrogeologic condition affected to the fractal dimension of the coal measure limestone reservoir. The results showed that the pore of the samples mainly were the micro mesoporous, the fractal dimension was between 2.666 9～2.840 3 and the average fractal dimension was 2.760 8.The pore fractal dimension was between the seam and sandstone reservoirs and was close to the fractal dimension of the shale reservoir. The limestone at the north east of Fault F7 had a higher fractal dimension and a higher heterogeneity. There was a positively related relationship between the fractal dimension and the matrix porosity and the negative related relationship between the fractal dimension and the pore volume. As for the coal measures limestone area in the developed water flow fault, the fractal dimension would be increased with the flow direction of the groundwater.