The kinetics of NDMA formation from dimethylamine hydrochlorate reacted with chloramine were studied. The correlation between the reactant concentration and reacting time was measured by the isolation method, and then the order of reaction, the reaction rate constant, and rate equation as well as the activation energy of dimethylamine hydrochlorate reacted with chloramine were obtained by the tentative method. The reaction of dimethylamine hydrochlorate with chloramine in first step to form an intermediate was second order and first order for both the salt and chloramine. The rate constants of dimethylamine hydrochlorate reacted with chloramines were 1.5361×10^-3, 1.8707×10^-3 and 7.7217×10^-3mol^-1·min^-1 at 5, 15 and 25℃, respectively. The reaction activation energy Ea was 51.27kJ/mol. The observed rate constants and the activation energy suggested that the reaction was better under high temperatures. Our results could provide experimental data for the reaction kinetics of dimethylamine and its derivatives with chloramines to form NDMA, and for the risk analysis of NDMA as disinfection by-products in the raw water treatment.