This invention relates to a two-phase integrated, multi-layered and internal-circulation anaerobic biological reactor. It is composed of: an upper inner casing, a middle inner casing and alower inner casing, a 1st gas-liquid separation reflecting plate, a 2nd reflecting plate, a 1st gas-isolation guiding plate, a 2nd gas-isolation guiding plate, an upper agitator, a lower agitator, liquid distributor and solid-liquid separator. Due to the equipped multiple inner circulation it makes the liquid being of fluidization condition, the anaerobic reaction is better than that of prior art method. This invention has advantages of: low area occupation, high load rate, high resistance of shock load, high efficiency, stable treatment, convenient operation, low operation cost, full sealed system of reactor, no bad odour, quick starting, short period of establishment, being suitable for the treatment of waste-water, waste-matter and waste-sludge in size of large, medium or small scale.