Seven kinds of sinters having different basicities were reduced at 900℃ with either 90%CO10%CO₂ gas mixture or Hz gas. The data were analyzed by the one-irrtertace unreacted-core model and the reduction rate changes by with CO and H: were compared. The results are summarized as follows;(1) The average reduction rates in H₂, were calculated from reduction curves between the reduction degree of 40% and 60% were 5∼7 times than that in CO except for one kind of sinter. (2) The ratio of the chemical reaction rate constant (Kc) between CO reduction and Hz reduction showed little difference except for one kind of sinter. The rate constants of Hz reduction were 2∼3 times higher than those of CO reduction. (3) the ratio of the effective diffusivity in the product layer (De) between CO reduction and H₂ Reduction was different among various sinters. The values of the effective diffusivity of H₂ reduction were 4∼14 times higher than Chose of CO reduction.