When we design a new process, decisions must be made by considering all the impacts on the environment throughout the whole product lifecycle. We propose a new method for the evaluation of product lifecycle using a systems approach. The method consists of two steps: First, total effect indexes on the environment are calculated; Secondly then the system is evaluated from the viewpoint in which the investigator is interested. With this method, we could avoid allocating the effects of an activity in a product lifecycle to several products, thus a process added to the product lifecycle system is evaluated, focusing on the effect in the whole system. As a case study, three recycle systems of PET bottle were analyzed from the viewpoints of CO, emission and crude oil consumption. We found that all three recycle systems were effective in reducing environmental impacts. As well, the increase of material recycle ratio from 0 to 25% is equivalent to the increase of the thermal recycle efficiency from 10 to 30%. Chemical recycle system reduces environmental impacts, though it consumes much energy in the recycle process. We present that our new method to evaluate product lifecycle system is effective for the design of chemical process incorporating environmental impacts.