Considering the seal and storage of gas, mechanical index of coal containing gas is usually obtained by normal three-axis experiment. While, according to national standard, mechanical index of coal is usually tested by uniaxial experiment. By utilizing the gas sealing system, an analogic uniaxial experiment method is proposed. Through designed experiments, the effect of gas on mechanical properties and mechanical response of the coal sample when effective confirming pressure is 0 is studied too. The experimental results show that pore gas changes the mechanical response of complete deformation stage, but the trend of change gradually weakens as the gas pressure increases, and it means that non-mechanical effects caused by absorbed gas play a leading role gradually.