Effects of high H-2 and H2O (steam) partial pressure (H-2 from 0 to 1.2 MPa, H2O from 2 to 1.2 MPa) on gasification rates of coal char and Ca-loaded coal char were investigated by using a thermogravimetric apparatus with the temperature range 923 K to 1,173 K. The gasification rate increased rapidly as the H-2 partial pressure was reduced in the reaction gases. The presence of H-2 gas strongly inhibited the char steam gasification rate. However, the gasification rate of Ca-loaded coal char was much higher than that of coal char, and the inhibition by H-2 of the gasification rate was smaller for Ca-loaded coal char than for coal char. The Langmuir-Hinshelwood model was used to analyze the effects of the H2O and H-2 partial pressures on char and Ca-loaded coal char gasification rates. The temperature-dependent activation energies k(a), k(b), and k(c) in the Langmuir-Hinshelwood model were obtained from experimental data and were used to simulate gasification rates for char and Ca-loaded coal char over a wide range of temperatures and P-H2/P-H2O ratios. The effects of H-2 partial pressure were greater (smaller) for Ca-loaded coal char than for char at 1,173 K (1,023 K).