The hydrogasification behavior of a Chinese bituminous coal with three different biomass char additives, i.e., sargassum char (SG char), saw dust char (SD char), and wheat straw char (WS char), was studied in a pressurized fixed bed reactor. The effects of the biomass char amount (0 to 30%), pressure (0.1 to 4 MPa), and temperature (973 K to 1073 K) on hydrogasification reactivity of coal were investigated. The results showed that the SD char and WS char improved the hydrogasification reactivity of coal noticeably, but for the SG char, the improvement at 973 K was not obvious because of the high content of chlorine. For all samples, the hydrogasification reactivity increased with increasing temperature and pressure. Moreover, experiments involving coal with different ash of biomass chars were conducted to verify the catalytic effects of alkali and alkaline earth metal (AAEM) species in the biomass char.