Valuating the function of ecosystem services is crucial for accounting green GDP, making a conserva-tion policy of ecological environment and the decision of regional development as well as sustainable development strategy. Rice-duck-fish symbiosis has been promoted in several developing countries as a way of&creasing incomes for rice farmers, but investigations of its value have mainly focused on direct economic benefits, such as food and raw material production. Few studies have been conducted on the estimation of indirect services provided by rice-duck-fish complex ecosystem. The gas regulation service and its economic values provided by rice-duck-fish complex ecosystem were studied in Wuhan, China. The major components of gas regulation are O2 emission and greenhouse, gases (GHGs, CO2) regulation. The results show that O2 emission from different treatments (including rice-duck (RD) rice-fish (RF), rice-duck-fish (RDF) and rice (CK)) ranged from 26,370 kg/ha to 33,910 kg/ha per year, with an eco- nomic value of 10,050-12,920 yuan/ha per year (Chinese currency: I euro=10.2475 yuan, August 28, 2007). The net GHGs exchange varied from 1,200 to 3,320 kg/ha per year, and its economic value ranged.from 1,040 yuan/ha to 2, 900 yuan/ha per year Consequently, the total economic value of gas regulation provided by symbiosis complex ecosystems ranged from 11,090 yuan/ha to 15,820 yuan/ha per year, and the maximum overall economic value of gas regulation was provided by RDF complex ecosystem. The work will be useful for further understanding of the func tions of rice-duek-fish complex ecosystem services and supplying the theoretical references to agricultural policy.