Hospital wastewater is a substance of concern because it can be a serious environmental pollutant and it can be harmful to human life. Top concerns for the wastewater discharged by the hospital are suspended solids SS (mg/L). organic matter such as BOD20/5 and COD (mg/L). and disease-causing bacteria such as E. coli, Sallmonella and coli forms. Disease-causing bacteria can survive for a certain time in the environment and there is the possibility that they could survive and thrive on a living host with a resulting spread of that particular infectious disease. This is why hospital wastewater is different from other wastewater. In the recent years, a biocide on the base of guanidine compounds, guanidine hydrochloride as oligohexametylene (OHMG) and guanidine hydrochloride polyhexametylene (PHMG), has been used in many areas because these two substances are environmentally friendly. Oligohexamethylene guanidine hydrochloride (OHMG) has received more attention because it is a strong bactericide and can be used to clean water, and OHMG itself is not treat and antioxidant. In this paper, the authors present the results of an evaluation of bactericidal effect of OHMG when it is applied to wastewater from Duc Giang Hospital.