The invention discloses a double-membrane wastewater biological treatment system. The double-membrane wastewater biological treatment system comprises a pool (case) body, a pretreatment zone, a biomembrane reaction zone and a membrane separation reaction zone; and all the above zones are separated through a wall or a separator to form respectively independent work systems, relevant zones are communicated through water flowing ports, a high pressure fan, a membrane water outlet pump and an ultraviolet ray disinfection instrument are arranged outside the pool (case) body, and water discharged from a membrane assembly is pumped into the ultraviolet ray disinfection instrument through the membrane water outlet pump, is disinfected and is discharged outside. The wastewater biological treatment system has the advantages of simple technological structure, good treatment effect, stable running and wide application range, is suitable for the low-concentration organic sewage treatment in hospitals, health centers, rural, the country and towns, and is also suitable for the high-concentration organic wastewater treatment in the industries of bave wastewater, slaughtering wastewater, food processing and the like, so treated water reaches recycled water reuse standards, accords with Chinese energy saving, emission reduction and circular economy policies, and the system can well play an important role in the public campaigns of Wild China, Urban and Rural Cleaning at present, and has large social and economic benefits.