Abstract: The measurement of effective diffusivity for KD306type sulfurtolerant methanation catalyst has been carried out through the Single Pellet String Reactor technique based on the computer sampling system developed by ourselves. The results of linearity processing are in good agreement with the solutions of parameter estimation method, which shows: linearity processing is reasonable and parameter estimation method can be used to determine the effective diffusivity. The most reasonable value of tortuosity factor for KD306type catalyst is 7.2