Modern agriculture not only brings high yield of grain but also produces many ecological and environmental problems, which urges people to turn their attention to traditional agriculture again. Some traditional agricultural systems not only have outstanding economic, social and cultural values, but also have a variety of important ecological functions, such as GHG emission reduction. Howev er, there were rarely studies to estimate the carbon sequestration and emission reduction capacities of traditional agricultural systems and evaluate their environmental impacts throughout their life cycles. Therefore, the carbon footprint of the rice-fish culture system in Qingtian county, Zhejiang province was measured by life cycle assessment based on the data of farmer surveys, and was compared with that of the local rice monoculture system. The results showed that: (1) the carbon footprints of Qingtian rice-fish culture system and rice monoculture system were 6266.7 kgCO₂-eq/hm² and 7520.0 kgCO₂-eq/hm², respectively, while the carbon footprints of output per unit were 0.12 kgCO₂-eq/yuan and 0.21 kgCO₂-eq/yuan, respectively. Compared with the rice monoculture system, the rice-fish culture system emitted less greenhouse gas, had less environmental impact, and had higher ecological and economic benefits. (2) The CH₄ accumulated in the agricultural production was the main source of carbon footprint, and the fertilizer input to agricultural production materials was the second source of carbon footprint. Feed from agricultural inputs was another important source of carbon footprint of rice-fish culture system. Quantifying the environmental impact of rice-fish culture system in Qingtian by carbon footprint method not only enriches the applicable types of carbon footprint in practical application, but also has reference significance for environmental impact assessment of other traditional agricultural systems.