NOVELTY - Method for preparing biogas using high concentration organic waste, involves selecting fermentation raw materials, crushing organic waste, adding the components into temperature adjustment tank, and at the same time adding fermented slurry to tank, stirring mixture and adjusting temperature inside tank, (b) feeding the processed material into a transport pipeline, (c) feeding high concentration organic materials into anaerobic fermentation tank, and (d) adding inoculum after fermentation back to tank, and other raw materials, and performing anaerobic fermentation.    USE - The method is useful for preparing biogas using high concentration organic waste (claimed).    ADVANTAGE - The method consumes less energy.    DETAILED DESCRIPTION - Method for preparing biogas using high concentration organic waste, involves (a) selecting fermentation raw materials, crushing organic waste, adding the components into temperature adjustment tank, and at the same time adding 5-10 times fermented slurry to the temperature adjustment tank, stirring the mixture and adjusting temperature inside tank to 40-55 degrees C, (b) feeding the processed material into a transport pipeline, (i) starting feed stage through a vertical feeding pipeline on top part of fermentation tank, and transporting inoculum, or (ii) feeding using a control valve that controls three vertical fermentation tank, where feed time ratio through top inlet and center of inlet is 1.2-1.5:1, (c) feeding high concentrations organic materials into anaerobic fermentation tank, where feed residence time is 15-30 days, and (d) adjusting the control valve using reflux clinker, adding inoculum after fermentation back to the temperature adjustment tank, and other new raw materials in a weight ratio of 5-10:1, and performing anaerobic fermentation. An INDEPENDENT CLAIM is included for fermentation system which comprises temperature adjustment tank, feed pump, vertical feeding pipeline and pump, conditioning tank, control valve, reflux clinker, gas outlet and gas pipeline.