NOVELTY - Agricultural ecological circulation system comprises farmland system, pig farming system, nursery stock for vegetable seedlings and special ecological cultivation system. The farmland system comprises multiple lands for production of raw materials e.g. corn, barley and wheat. The pig farming system includes farms for pig, anaerobic digesters maintained at room temperature, mesophilic digester tank and heating boiler. The nursery stock for vegetable seedling comprises plantation, vegetable and flower garden, lotus pond, and land for fruit tree and forest.    USE - The agricultural ecological circulation system is useful for producing marsh gas which is used as fertilizer, preferably organic fertilizer for vegetable crops, nursery stock, fruits e.g. melon, lotus root, and farmland. The marsh gas energy is used for centralized gas supply and heating boiler. The marsh gas slurry is used as fertilizer for vegetable seedlings, and fruits e.g. melon and lotus root (claimed).    ADVANTAGE - The agricultural ecological circulation system has efficient zero emission and hence does not cause environmental pollution, and efficiently utilizes waste materials.    DETAILED DESCRIPTION - Agricultural ecological circulation system comprises farmland system, pig farming system, nursery stock for vegetable seedlings and special ecological cultivation system. The farmland system comprises multiple lands for production of raw materials e.g. corn, barley and wheat. The pig farming system includes farms for pig, anaerobic digesters maintained at room temperature, mesophilic digester tank and heating boiler. The nursery stock for vegetable seedling comprises plantation, vegetable and flower garden, lotus pond, and land for fruit tree and forest. The special ecological cultivation system includes fish pond and understory backyard farms. The pig farming land is prepared by (i) obtaining pig excrement as raw material, subjecting the pig excrement to solid-liquid separation, passing the liquid to anaerobic digester, and performing anaerobic methane fermentation in the anaerobic digester at room temperature and ambient temperature to produce marsh gas, where a portion of obtained marsh gas slurry is used for immersing crop straw, and fruit and vegetable wastes, and other portion marsh gas slurry is used as fertilizer, and feces is used as organic fertilizer for vegetable seedlings and fruit tree, (ii) passing immersed crop straw, and fruit and vegetable wastes to mesophilic digester tank for performing anaerobic fermentation to produce marsh gas, where the marsh gas residue is processed to obtain organic fertilizer. The nursery stock plantation enables production of vegetable seedlings, flower seedlings and fruit tree seedlings. The vegetable seedlings, flower seedlings and fruit tree seedlings are transplanted to greenhouse or land, providing fruit and vegetable wastes, and poultry waste to the seedlings. The lotus pond enables cultivation of lotus. The fish pond farms fish using the fruit and vegetable wastes, and poultry waste as fish feed.