Abstract: The kinetics of the hydrogenation of benzene to cyclohexane in liquid-phase is studied by using a new kind of Ni/Al2O3 catalyst after eliminating the external and internal diffusion influence at the temperature range of 433-473 K and pressure range of H2 of 0.6-3.3 MPa. Research shows that the reaction is zero-order for benzene while first-order for hydrogen. Therefore, the main reason of the internal diffusion resistance comes from the hydrogen diffusion in catalysts. The internal efficiency factor and Thiele modulus demonstrate that the internal diffusion resistance can only be eliminated when the particle diameter is smaller than 0.150 mm, which implies the high activity of the catalyst. The effective diffusion coefficient of hydrogen in the liquid phase is determined from the definition equation of the Thiele modulus. The comprehensive diffusion coefficient for hydrogen in the liquid is calculated by the Wilke-Chang equation, and the tortuosity factor of the catalyst is obtained to be 3.12 from the definition equation of the Thiele modulus. The radial distribution profile of hydrogen concentration in the liquid phase in the particles with different sizes indicates that the internal diffusion resistance of hydrogenation is the controlling factor.