Abstract: The magnetic nanometer solid superacid SO42-/TiO2-Fe3O4 was prepared by sol-gel method, and its catalytic activity on reaction between rosin acid and glycerol was examined under different preparing conditions. Thus, ratio of Ti and Fe (30:1), soaking the magnetic nanometer powder in 1.5 mol/L H2SO4 and calcining at 450℃ for 3 h were the optimum preparing conditions. The structure of the catalyst was characterized by IR and TEM. Acid intensity of this catalyst was measured by improved Hammett indicator method.