NOVELTY - A combined ammonia stripping and absorption and biogas purification and desulfurization method comprises (A) ammonia stripping and absorption; (B) sterilization of Escherichia coli excrement; and (C) biogas purification and desulfurization. The step (B) comprises opening first three-way electromagnetic valve, where stripping tower includes sterilizing device liquid inlet pipe, introducing liquid to sterilizing device and killing Escherichia coli, opening second three-way electromagnetic valve and liquid pump, and introducing biogas slurry.    USE - Combined ammonia stripping and absorption and biogas purification and desulfurization method.    ADVANTAGE - The method reduces processing pH and hardness of the biogas slurry.    DETAILED DESCRIPTION - Combined ammonia stripping and absorption and biogas purification and desulfurization method comprises (A) ammonia stripping and absorption; (B) sterilization of Escherichia coli excrement; and (C) biogas purification and desulfurization. The step (A) comprises:    (A) opening first electromagnetic valve (3), introducing anaerobic fermentation liquid by biogas slurry conveyer pipe into stripping tower (4) from the top, starting electric stirring device (5), automatic measuring additive into stripping tower, adjusting pH value of biogas slurry;    (B) starting air pump (7), performing gas-liquid exchange in stripping tower of ammonia with biogas liquid by mass transfer and stripping effect;    (C) implementing additive in biogas liquid phosphorus and organic flocculating and precipitating process, and blowing out ammonia from biogas by circulating gas conveying pipe with recycle gas (8); and    (D) introducing ammonia absorption tower from bottom, starting second liquid pump, liquid conveying pipe water distributor from ammonia gas absorption tower, and performing liquid mass transfer and absorbing ammonia.    The step (B) comprises opening first three-way electromagnetic valve, where stripping tower includes sterilizing device liquid inlet pipe, introducing liquid to sterilizing device and killing Escherichia coli, opening second three-way electromagnetic valve and liquid pump, and introducing biogas slurry into high temperature heat exchange device. The step (C) comprises introducing biogas liquid to stripping tower, starting third liquid pump, introducing into marsh gas purifying device, opening second electromagnetic valve, purifying marsh gas by marsh gas purifying device, and blowing off hydrogen sulfide and carbon dioxide biogas.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic diagram illustrating a combined ammonia stripping and absorption and biogas purification and desulfurization method.    First electromagnetic valve (3)    Stripping tower (4)    Electric stirring device (5)    Air pump (7)    Recycle gas (8)