NOVELTY - A biogas generator comprises material tank (10), acidifying tank (15), downward flow type air tank (16), upflow type anaerobic air producing tank (18) and rear storage tank (19). Upper parts of acidifying tank, downward flow type air tank, upflow type anaerobic air producing tank and rear storage tank are provided with tapered sections. The charging pipe and biogas liquid outlet pipe are respectively assembled on tapered section of acidifying tank and tapered section of rear storage tank. The discharging opening of charging pipe is positioned at upside position of acidifying tank.    USE - Biogas generator for hydraulic conveying.    ADVANTAGE - The generator has simply structure, has little power energy consumption when operating and running, has little operation failures, has fast anaerobic fermentation speed but high air producing speed. It can comprehensively and accurately display measurement and is convenient to use.    DETAILED DESCRIPTION - Biogas generator comprises material tank (10), acidifying tank (15), downward flow type air tank (16), upflow type anaerobic air producing tank (18) and rear storage tank (19). Upper parts of acidifying tank, downward flow type air tank, upflow type anaerobic air producing tank and rear storage tank are provided with tapered sections. The charging pipe and biogas liquid outlet pipe are respectively assembled on tapered section of acidifying tank and tapered section of rear storage tank. The discharging opening of charging pipe is positioned at upside position of acidifying tank. The charging opening of biogas liquid outlet pipe is positioned at bottom side of rear storage tank. Charging opening and discharging opening of charging pump are respectively connected with material tank and charging pipe. Charging opening of reflux agitating pump is communicated with downward flow type air tank, upflow type anaerobic air producing tank and rear storage tank. First hydraulic conveying overflow pipe, second hydraulic conveying overflow pipe and third hydraulic conveying overflow pipe are respectively arranged between acidifying tank and downward flow type air tank, between downward flow type air tank and upflow type anaerobic air producing tank and between upflow type anaerobic air producing tank and rear storage tank. The first hydraulic conveying overflow pipe is mounted on tapered sections of acidifying tank and downward flow type air tank. The second hydraulic conveying overflow pipe is mounted on tapered sections of downward flow type air tank and upflow type anaerobic air producing tank. The third hydraulic conveying overflow pipe is mounted on tapered sections of upflow type anaerobic air producing tank and rear storage tank. Charging opening of first hydraulic conveying overflow pipe is positioned at bottom side of acidifying tank and discharging opening is positioned at upper part of downward flow type air tank. The charging opening and discharging opening of second hydraulic conveying overflow pipe are respectively positioned at bottom side of downward flow type air tank and that of upflow type anaerobic air producing tank. The charging opening and discharging opening of third hydraulic conveying overflow pipe are respectively positioned at upper side parts of upflow type anaerobic air producing tank and rear storage tank. Pipelines of first, second and third hydraulic conveying overflow pipe are assembled with flexible connecting pipes. Upper parts of tapered sections of acidifying tank, downward flow type air tank, upflow type anaerobic air producing tank and rear storage tank are assembled with air storage chamber with air outlet pipe and air return pipe. Charging opening pipeline of charging pump and reflux agitating pump are respectively mounted with clean water pipe with valve. The valve is controlled by valve controller to open and close.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic diagram illustrating a biogas generator.    Material tank (10)    Acidifying tank (15)    Downward flow type air tank (16)    Upflow type anaerobic air producing tank (18)    Rear storage tank (19)