Performance of NiO-MgO solid solution with the promoting effect of noble metals such as Rh, Pt and Pd on catalytic activity and carbon deposition were investigated in oxidative steam reforming of methane under atmospheric and pressurized conditions. At low W/F condition such as 0.13 gh/mol, small amount of noble metals promoted Ni0.2Mg0.8O exhibited much higher catalytic activity than Ni0.2Mg0.8O catalyst which was showed combustion activity due to the oxidation deactivation in oxidative steam reforming of methane under atmospheric pressure. In the case of TPR profiles, reduction degree of Ni over noble metals catalysts was more effective to the high catalyst reducibility than that on NiO-MgO solid solution. Under pressurized conditions, large amount of carbon was formed on Ni0.2Mg0.8O; where as, the amount of deposited carbon was negligible on Rh catalyst. Especially, small amount of Rh addition such as 0.035 % Rh/Ni0.2Mg0.8O catalyst is extremely stable and it is completely inhibited the carbon deposition under pressurized conditions in oxidative steam reforming of methane.