Trihalomethanes, produced as a result of chlorination of drinking water, are considered a potential health hazard. More than 80% of water treatment plants use chlorine as a disinfectant. Trihalomethane formation (THMF) of a raw water source may indicate the maximum trihalomethanes (THMs) that are likely to be produced when chlorine reacts with natural organic matter (NOM) present in the water. Trihalomethanes, a family of halogenated disinfection by-products, are prevalent in finished packing drinking water. Trihalomethanes have been known as carcinogen material for human by IARC. According to USEPA’s Disinfectants and Disinfection By-products Rules (DBPRs), the regulatory standard of the total trihalomethanes (TTHMs) is 80 μg/L. This research was conducted to evaluate and compare the level of TTHMs in the concentration of chlorine dose in varies samples, ranging from 80 ml to 200 ml of 10% chlorine dose. Gas chromatography technique was used in with electron capture detector for analyzing samples of THM for each of the four main THMs species measured are CHCl3 (Chloroform), CHCl2Br (Bromodichloromethane), CHClBr2 (Dibromochloromethane), and CHBr3 (Bromoform). Besides, a purposive survey for the evaluation of knowledge, attitude and practice (KAP) about THMs were conducted in four bottling waters. Mean concentration of total THMs in the samples related to the concentration of chlorine dose varies in the samples, ranging from 80 ml to 200 ml of 10% chlorine dose were determined 0.00093,0.0044, 0.0069and 0.7 mg/l , respectively. THM concentration in four different doses of chlorine varies in the samples was compared by using regression test, which represents an significant difference between total THMs concentration at different dose of chlorine. Dose change was observed in the present study. On the other hand the knowledge, attitude and practice towards by products specifically THMs in industrial bottling water producers’ minority of them know the risk of THMs. In conclusion, the data suggests that there's a correlation between chlorine dose and THMs concentrations, with higher doses resulting in higher THMs levels. This highlights the importance of balancing disinfection requirements with the need to minimize potentially harmful disinfection by-products like THMs in drinking water. Monitoring, controlling, and potentially optimizing the chlorine dose can help in maintaining THMs concentrations within safe limits. Keywords: chlorination, Disinfection By-Products, Trihalomethanes, KAP,Bottling water