NOVELTY - Regulating and controlling parameter of grade-by-type marsh gas grade lifting system involves taking grade-by-type marsh gas grade lifting system composed of multi-level optical bioreactor in series, each stage of reactor by using carbon dioxide micro-algae in a marsh gas, staying marsh gas for a certain time in each level reactor to a reactor, gradually lifting marsh gas grade, gas-liquid ratio, level of each stage of reactor, marsh gas residence time and microalgae initial inoculating amount, which is a key parameter of the system.    USE - For regulating and controlling parameter of grade-by-type marsh gas grade lifting system (claimed).    ADVANTAGE - The method allows regulating and controlling parameter of grade-by-type marsh gas grade lifting system. The key parameter can improve benefit of the whole system. The parameter of system level allows determining the complexity of the construction cost and operation of the system, at the same time, the working time of the whole system. The method improves the grade of the marsh gas and purifies the biogas slurry.    DETAILED DESCRIPTION - Regulating and controlling the parameter of grade-by-type marsh gas grade lifting system involves taking grade-by-type marsh gas grade lifting system composed of multi-level optical bioreactor in series, each stage of reactor by using carbon dioxide micro-algae in a marsh gas, staying the marsh gas for a certain time in each level reactor to a reactor, gradually lifting marsh gas grade, gas-liquid ratio, level of each stage of reactor, marsh gas residence time and microalgae initial inoculating amount, which is a key parameter of the system. The initial inoculating amount is controlled in the range of 80-400 mg, the range of marsh gas residence time is controlled in the range of 48-72 hours, level number is controlled in the range of 8-11, and gas-liquid ratio is controlled in the range of 10:1 to 6:1. The system adopts artificial light source LED lamp and/or natural light source sunlight.