To investigate the feasibility of a chemical-looping hydrogen generation system, we investigated the reduction and water splitting reaction characteristics for three mediators and two reducing gas in a bubbling fluidized bed reactor (0.02 m I.D.). For three oxygen carrier particles (NiO/bentonite, Fe2O3/bentonite, (NiO : Fe2O3)/bentonite), hydrogen was used as a reduction gas and water was used as an oxidation gas. For (NiO : Fe2O3)/bentonite particle, carbon monoxide, which is the main component in the syngas from coal or heavy residue, was used as a reducing gas to check reactivity for the carbon containing fuels and carbon deposition characteristics. Based on the reactivity tests, (NiO : Fe2O3)/bentonite particle was selected as the best mediator for the chemical-looping hydrogen generation system to achieve stable continuous operation.