Abstract: This paper gives an analysis on the economic and ecological effects of fish culture in paddy fields in northern Zhejiang province.In the system the rice field provided favorable living conditions for fish, and fish consumed weeds and rice insects, controled rice disease, improved soil fertility and rice growth.The rice yield and the output-input ratio of energy were increased by 9.3% and 14.2% respectively.The fish production and the total income were reached to 1384.5kg/ha and 4981.5 yuan/ha respectively.

Key words: Coal fly ash, Shajiang black soil, Ecological factor, Residue, Soil amended