Abstract: To understand the stability of HAcAms (haloacetamides) in water, two brominated species including BCAcAm (bromochloroacetamide) and DBAcAm (dibromoacetamide), and two chlorinated species including DCAcAm (dichloroacetamide) and TCAcAm (trichloroacetamide), which were commonly detected in drinking water and reclaimed water, were selected as targeted HAcAms. The stability of the targeted HAcAms was examined under a variety of conditions including different pH, initial concentrations of HAcAms, temperatures and disinfectant doses including chlorine doses and monochloramine doses. The results indicated that the targeted HAcAms were stable at pH 5 and 7, but all of them underwent alkaline hydrolysis in the pH range of 8 to 10 with hydrolysis rates rising with increasing pH values. Among the 4 HAcAms, the hydrolysis rates followed the order TCAcAm > DCAcAm > BCAcAm > DBAcAm under the same alkaline conditions. Besides, the hydrolysis rates of the HAcAms increased with the decrease of initial HAcAms concentrations in the range of 30 to 150 μg/L and the increase of temperature in the range of 25 to 35℃. At neutral condition, the doses of free chlorine in the range of 1 to 5 mg/L caused rapid loss of HAcAms, and the rates of loss accelerated with increasing chlorine dose. This chlorine-assisted reaction followed the trends noted for HAcAm alkaline hydrolysis. At pH 7, the HAcAms were stable when monochloramine concentration was in the range of 0.5 to 5 mg/L. In conclusion, the 4 HAcAms could undergo hydrolysis at high pH, low initial concentrations of HAcAms, high temperature, and undergo degradation in the presence of chlorine. The brominated HAcAms exhibited higher stability than the chlorinated compounds, thus more attention should be paid to them.