1.School of Resources and Geosciences，China University of Mining and Technology，Xuzhou , China；2.Research Institute of Petroleum Exploration & Development,PetroChina, Langfang , China；3.PetroChina Huabei Oilfield ,Renqiu ,China

In order to find out the effect of different stress load on coal-rock permeability sensitivity, the pulse decay method had adopted to observe the permeability changes with the stress by respectively changing confining pressure and pore pressure. Meanwhile, stress sensitivity mechanism was analyzed from the perspective of pore structure. The results showed that the pulse-decay method was suitable for the stress sensitivity experiment of low permeability coal samples. Moreover, the coal rocks entirely showed strong stress sensitivity to different stress changes in the exponent attenuation. The stress sensitivity to confining pressure changes was stronger than that to pore pressure changes during confining pressure increasing first and then decreasing, the stress sensitivity to increasing confining pressure was stronger. The stress sensitivity mechanism of coal rocks was mainly caused by the changes of coal rock cuttings and pore throats resulting from the stress changes. Samples of low permeability mainly developed by small holes and throats showed stronger sensitivity as the pores were easier to compress and block and the permeability decreased rapidly.