Abstract: In order to make sure the reaction mechanism of manganese tetroxide (Mn<SUB>3</SUB>O<SUB>4</SUB> ) prepared by oxidation with suspension solution catalyzed by acids，reaction kinetics was studied with differential method and chemical method when catalyzed by HCl.Meanwhile,the impacts of different manganic complexes generated in different acid solutions on the reaction rate were investigated.Result proved that the reaction was a first order in metallic manganese.At 323 K,apparent rate constant was 1.13×10<SUP>-4</SUP>s<SUP>-1</SUP>.And the stability of manganic complexes had obvious effect on the reaction rate,compared with HCl system,nitrilotriacetic acid and EDTA systems slowed down the reaction rate and organic acid system speeded up the reaction rate.&nbsp; 