Due to high proportion of plastics in the solid waste, Environmental Protection Administration (EPA) implemented ”Limited Usage Policy of Plastic Shopping Bags” since July 1, 2002 to reach the goal of plastic bags reduction. However, how could it really reduce environmental impact while this policy was implemented? Or, could it cause more danger to whole or local natural environment? Therefore, Life Cycle Assessment (LCA), a scientific, objective and effective method, was used to evaluate the plastic bags and shopping bags provided and sold by 7-11, Family convenient shops and RT-MART, Carrefour hyper-marts before and after this policy was implemented. In this study, both analysis and comparison matched with disassembly, inventory and interview would be carried out after considering resources consumption, purchasing cost, proportion and times of reuse and price policy to analyze the environmental impact of the shopping bags with life cycle assessment software SimaPro. The results of the study were shown as follows: In the study, Simapro software was needed for LCA analysis. After normalization, the environmental impact for shopping plastic bags were evaluated based on per time use. The environmental impact caused by shopping bags, which is provided by convenient shops, was evaluated for each time use under equal capacity. The environmental impact of the middle plastic bags provided by 7-11 convenient shops was 2.02 mPt and the most harmless one to environment. The next one was the 2.27mPt of large plastic bag provided by 7-11 convenient shops. The environmental impact of the No. 20 plastic bags provided by Family convenient shops was 2.70 mPt, and the most harmful to environment. For the shopping bags provided by hyper-marts, the shopping bag of no-woven fabric material had 1.44 mPt of environmental impact, which was the most harmless one to environment. The next one was the PE material shopping bags (2.06mPt). And the worst one was the shopping bags of nylon material that had 6.54 mPt of environmental impact. For the three stages of manufacturing, distribution and sale, and discarding of product, the manufacturing stage, which occupied about 9599% of total environmental impact, is the highest. For the environmental impact of three aspects of whole life cycle, the environmental impact of resources consumption aspect provided by plastic bags sold by convenient shops and shopping bags sold by hyper-marts, occupied about 70% of all environmental impact. The next aspect is human health, which occupied about 25%. For the energy consumption aspect, the energy consumption of plastic bags provided by convenient shop occupied about 70% of total environmental impact; and the bigger plastic bags were provided, the smaller environmental impact for energy consumption would be caused. For the energy consumption of shopping bags provided by hyper-marts, the environmental impact of nylon shopping bag was the highest, 5.1 5mPt; the next high ones were thick plastic bag and PE shopping bag. For the plastic bag sold by convenient shops, the large plastic bag sold by 7-11 convenient shops was the most economic one because, compared with other plastic bags, it had the same price, the maximum capacity and its average usage price was only 0.3ONT＄. For the shopping bags sold by hyper-marts, thick plastic bag was the most economic one, just 0.22 NT＄ for per time use, the next one was no-woven shopping bag that was 0.53NT＄. And nylon shopping bag was the most expensive one of 1.73NT＄ for per time use. But the most economic one was not just the same one of more environmental protection.