Chlorination as a disinfection process is often used for disinfecting hospital wastewater in order to prevent the spread of pathogenic microorganisms and causal agents of nosocomial infectious diseases, but harmful byproducts might be formed and cause adverse ecological and health effects. In this study, the generation of trihalomethane (THMs) in the effluent of hospital wastewater during chlorine disinfection process was evaluated. The results showed the formation of THMs increased gently along the increasing chlorine dosages at beginning of the chlorine disinfection, but increased significantly after the chlorine dosages over 20 mg/L. Chloroform was the most abundant THM species and occupied above 40% of the total concentration. The second-order model interpretation of the long-term formation of THMs showed a good linearity and a second-order rate constant of 0.8857 (mg/L)-1s-1 in this experiments. Additionally, THM formations in these water samples well correlated with SUVA with generally exponential (R =0.9987).