We evaluated the environmental burdens of one existing composting system and four alternative composting systems with different turning frequencies in Beijing area using life cycle assessment(LCA). The results showed that resources consumption and atmospheric emissions played important roles in the environmental impacts of pig manure composting process. For these five composting options, fossil energy of 80.8 to 221.5 MJ was needed to compost one ton of pig manure. During composting, ammonia emissions contributed more than 96% to the acidification potential(AP) and eutrophication potential(EP). Carbon dioxide and N_2O from the pig farms contributed to about 58% to 88% and 8% to 35% of the total global warming potential, respectively. Of the alternative options, the options with turning frequency of 1 to 2 times per week with diesel-powered turning machine should be recommended for pig manure composting because of the lower environmental impacts.