The volumetric mass transfer coefficient kLa of gases(H2, CO, CO2) and mass transfer coefficient kLon liquid paraffin side were studied using the dynamic absorption method in slurry bubble column reactors under elevated temperature and elevated pressure. Meanwhile, gas-holdup and gas–liquid interfacial area a were obtained.The effects of temperature, pressure, superficial gas velocity and solid concentration on the mass transfer coefficient were discussed. Experimental results show that the gas–liquid volumetric mass transfer coefficient kLa and interfacial area a increased with the increase of pressure, temperature, and superficial gas velocity, and decreased with the slurry concentration. The mass transfer coefficient kLincreased with increasing superficial gas velocity and temperature and decreased with higher slurry concentration, while it changed slightly with pressure. According to analysis of experimental data, an empirical correlation is obtained to calculate the values of kLa for H2(CO, CO2) in the gas–paraffin–quartz system in a bubble column under elevated temperature and elevated pressure.