Abstract: In order to evaluate the gas resources of K₂, K₃ and K₄ limestone in 9^#, 8^# and 7^# coal seams of Yitang Coal Mine in Huoxi coal field, explain the large gas emission in the limestone reservoirs, ensure the subsequent exploitation of gas resources, through the survey of field geological environment and underground mine observations, as well as the data analysis of core recovery and drilling leakage, finally, we adopt the method of using the ratio of drilling leakage of three-layer limestone to limit the porosity which is calculated from core recovery. The macroscopic porosity of K₂, K₃ and K₄ limestone is estimated to be 20.10%, 14.81% and 10.58%. The results provide the explanation for large gas emission in the limestone reservoirs of Yitang Coal Mine.