From economic, environmental and social benefits, this paper analyzes the components of LID approach benefits in sponge cities. Economy factors include reducing energy consumption, recycling rainfall, and decreasing rainfall pipe operating cost. Environmental factors include purifying air, reducing carbon emission, compensating underground water. Social factors include reducing social investment in eliminating pollution, decreasing flooding cost. This paper uses environmental economics to study the monetization methods of LID approach benefits, and establishes net benefit indexes of LID approaches via full life cycle theory from perspective of cost and benefits. Taking sponge city Zhenjiang as an example, this paper quantitatively studies the comprehensive benefits of LID approaches in Zhenjiang, which receives economic benefits from saving water, saving power, reducing carbon emission, preventing pollution and preventing flooding, up to 6.53 RMB per square meter annually. This paper presents suggestions on improving compensation policy, boosting sponge city technical system, intensifying rainfall resource development, and rationally selecting LID approaches.