Catalytic dehydration of glycerol over solid catalysts provides a sustainable and economic route to producing acrolein. Unsupported MoP catalyst was prepared by temperature-programmed-reduction method and used for the gas-phase glycerol dehydration. The catalyst was characterized by means of XRD, SEM, TEM, NH3-TPD, PyIR, XPS, TG-DSC, and N-2 adsorption-desorption. It is indicated that the acidic P-OH and M-oOH groups, which are usually associated with the weak or moderate strength of Bronsted acid sites, were presented on the surface of MoP. The effects of reaction temperature and carrier gas flow rate on glycerol conversion and acrolein selectivity were investigated over MoP. The selectivity to acrolein was up to 89.0 % and kept constant in a 50-h run at 240 degrees C. The gradual decrease of glycerol conversion might be related to the insoluble carbonaceous materials deposited on the catalyst surface.