NOVELTY - An automatic circulating toilet flushing system using purified fermentation liquor, comprises a marsh gas tank (5), a feed basin (4), and a toilet (1); where an excrement outlet of the toilet is interconnected with a decontaminating septic tank (2); an outlet end of decontaminating septic tank is interconnected with feed basin; fence posts (17) are evenly distributed at an outlet of decontaminating septic tank; a discharge port of marsh gas tank is interconnected with a marsh gas discharge basin (6); and a filter screen (7) is set between marsh gas discharge basin and gravel filtering basin.    USE - The automatic circulating toilet flushing system using purified fermentation liquor is useful for industrial applications.    ADVANTAGE - The automatic circulating toilet flushing system using purified fermentation liquor solves the problem that the toilet is prone to be clogged with wastes because the excrement is directly discharged to the marsh gas tank, the waste is difficult to degrade, and less marsh gas is produced. Moreover, the filtered fermentation liquor is clean and odorless. Additionally, it makes the best of renewable sources, saves water for flushing the toilet, improves environmental sanitation, protects environment, promotes multipurpose use of the methane fermentations waste, and quickens rural economic development.    DETAILED DESCRIPTION - An automatic circulating toilet flushing system using purified fermentation liquor, comprises a marsh gas tank (5), a feed basin (4), and a toilet (1); where an excrement outlet of the toilet is interconnected with a decontaminating septic tank (2) through a pipeline; an outlet end of the decontaminating septic tank is interconnected with the feed basin; fence posts (17) are evenly distributed at an outlet of the decontaminating septic tank; a discharge port of the marsh gas tank is interconnected with a marsh gas discharge basin (6); one side of the marsh gas discharge basin is connected with a gravel filtering basin (8), a medium sand filtering basin (9), and a water purifying reservoir (10); a filter screen (7) is set between the marsh gas discharge basin and the gravel filtering basin; vent holes (11) are evenly distributed over the top surface of the water purifying reservoir; a water outlet of the water purifying reservoir is connected with a water pump; a water outlet of the water pump is interconnected with a water tank of the toilet through a water pipe (12); and the decontaminating septic tank has half the volume of the marsh gas tank.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the automatic circulating toilet flushing system using purified fermentation liquor.    Toilet (1)    Decontaminating septic tank (2)    Feed basin (4)    Marsh gas tank (5)    Marsh gas discharge basin (6)    Filter screen (7)    Gravel filtering basin (8)    Medium sand filtering basin (9)    Water purifying reservoir (10)    Vent holes (11)    Water pipe (12)    Fence posts (17)