NOVELTY - Bi-phase pressure anaerobic fermentation processing of perishable waste for preparing marsh gas, involves performing acidification reaction on the perishable waste, performing methanation reaction on acidic liquid and gas in methanation reactor, mixing the marsh gas with the methane digestive juice after methanation reaction is stable, adjusting pH value, and performing the methanation reaction on the acidic gas and the mixed liquid.    USE - The method is useful for performing bi-phase pressure anaerobic fermentation processing of perishable waste which is useful for preparing marsh gas (claimed).    ADVANTAGE - The method produces marsh gas with high yield and high purity, does not make use of cleaning and purifying system. The system is strong in stability, and anti-shock loading capability.    DETAILED DESCRIPTION - Bi-phase pressure anaerobic fermentation processing of perishable waste for preparing marsh gas involves (a) performing acidification reaction on the perishable waste in an acidification reactor to obtain an acidic gas and acidic liquid, and triggering the acidification reaction at the beginning stage of reaction, where acidification is performed by loading organic materials having pH value of 4-6 at a rate of 10-20 kgVS/m3/d for hydraulic retention time of 3-8 days at a reaction temperature of 30-40 degrees C or 50-60 degrees C, (b) performing methanation reaction on acidic liquid and gas in methanation reactor to obtain marsh gas and methane digestive juice, and triggering the methanation reaction at initial stage of reaction, where methanation reaction is performed by loading organic materials having pH value of 6.8-8 at a rate of 1-3 kgVS/m3/d for hydraulic retention time of 10-20 days at a reaction temperature of 30-40 degrees C, and (c) mixing the marsh gas with the methane digestive juice in a mass ratio of (14:1)-(2:1) after that the methanation reaction is stable, adjusting the pH value, and performing the methanation reaction on the acidic gas and the mixed liquid in the methanation reactor to obtain marsh gas and methane digestive juice. An INDEPENDENT CLAIM is included for system for processing of perishable waste for preparing marsh gas which comprises acidification reactor, acidification gas storage tank, acidification buffer tank, methanation reactor, methanation buffer tank, where the acidification reactor is provided with inlet, gas outlet, and liquid outlet, the methanation reactor is provided with gas inlet, liquid inlet, gas outlet, and liquid outlet, gas inlet of the acidifying gas pipeline and storage tank is connected to acidification reactor, and the acidifying gas storage tank outlet and the methanation reactor is connected to the gas inlet.