A vertical flow constructed wetland that had 70 m~3/d processing capacity was applied as the evaluation subject,a life cycle assessment on construction stage and running stage for global warming,acidification,eutrophication, photochemical ozone synthesis and dust &solid waste were evaluated based on 1 m~3 wastewater treatment unit. Results show that:the main contributors to global warming were CO_2 and N_2O which were discharged from construction stage,accounting for 82.2%;the main contributor to acidification was NO_x which was discharged from construction stage,accounting for 70.1%;the main contributors to eutrophication were total nitrogen,ammonia nitrogen and total phosphorus which were discharged from running stage,accounting for 89.4%;the main contributor to photochemical ozone synthesis was CH_4 which was discharged from running stage,accounting for 77.5%;dust &solid waste were discharged from construction stage.The environment impact index showed that eutrophication>photochemical ozone synthesis>dust &solid waste>global warming>acidification.