The structure parameters of gas transport for the oxide pellet were obtained by the modified Wicke-Kallenbach method(abbreviated as W-K method in the present paper). The specimens are acid pellet, basic pellet. Reduction was conducted in CO-CO_2 gas mixtures in stepwise manner. The change of pore structure of the sample during the stepwise reduction was observed with the mercury porosimetry. Samples in a single particle were also reduced to observe the weight change during the stepwise reduction and the effective diffusivity was derived by applying the unreacted core model. Thus obtained values by different methods was compared with that by W-K method. The results are summarized as follows 1. Temperature dependence of parameters for the reduced phases as well as original sample of acid and basic pellets were determined at 850, 950, 1050℃ Thus obtained values display not the clear relation with temperatures but a tendency to a gradual increase with increasing temperature. 2. The porosity and average radius of the original and reduced phase of pellets were observed with the mercury porosimetry. These obtained values do display a tendency to a gradual increase with increasing temperature. 3. Good accordance was found between the effective diffusivity of pellets by using the unreacted core model and that obtained from W-K method except some cases in acid pellets.