In this report the decomposition and oxidation kinetics of thiourea dioxide and thiourea trioxide are investigated with a reversed-phase ion-pair high-performance liquid chromatography (HPLC) method.The HPLC method allows us to simultaneously determine and quantify several sulfur-containing reagents such as (NH2)2CSO2,(NH2)2CSO3,(NH2)2CO,and SO32- (HSO3－). Experiments illustrate that the decomposition of thiourea oxides is a first-order reaction,in which the rate constants increase with the pH of the solution.Oxidations of thiourea oxides by hydrogen peroxide are first order with respect to both reagents within the studied pH range between 4.0 and 8.0.Oxidation rate constants are measured under different pH conditions,which show that increasing the pH of the reaction solution significantly accelerates the oxidation process