To illuminate the environmental impacts of the secondary pollution in wastewater treatment and facilitate scientific supervision,this research takes a pharmaceutical wastewater treatment process in Harbin as an example,and quantitatively analyzes the environmental impact load of the whole process using life cycle assessment(LCA) methods. In the impact assessment phase,improved analytic hierarchy process (AHP) is used to determine the indicator weights. Weighting assessment results show that the impact on depletion of non-renewable resources is the largest,followed by land filling space,potential human health effects,global warming potential ( GWP),water eutrophication ( EU),acidification potential( AP),air quality potential (AQP),and photochemical ozone creation potential(POCP). The improvement measures for the reduction of resource consumption and pollutant emissions are proposed to make wastewater treatment play more environmental benefits.