As pollution causes a series of problems with eco-environment,food safety and public human health,environ-mental risk assessment of contaminated sites has attracted extensive attention. Based on an investigation of a certain waterhead region for pollution of organic chemicals,like oils and benzene,heath risk assessment of drinking water in the region was performed using the MMSOILS model,a multimedia exposure assessment model,with Benzene as a target contaminant. The assessment shows that the total health risk value of Benzene contamination of drinking water in District A caused by the alkene plant is 9.94×10^-5,which is far too much higher than the U.S. EPA risk limit of 10^-6 and means that the contamination hazards public health. The contaminant comes mainly from the cracking installation,making the drinking water high in health risk value,being 9.82×10^-5,accounting for 98.8% of the total. According to the modeling results,risk value in District A will lower to 10^-6,posing no risk to human health,only after the Benzene concentration in the soil around the cracking installation is reduced to 1.32 mg kg^-1. The research results provide an important foundat ion for effective control of the pollution and remediation of the contaminated sites.