The invention discloses a nitrogen and phosphorus removal integrated biological reaction tank operating in multiple modes. The biological reaction tank comprises a biological selection zone, a pre-anoxic zone, a main reaction zone, a water distribution zone, a water outlet zone and an internal reflux channel, wherein the main reaction zone comprises a zone A, a zone B and a zone C; the zone A can serve as an anaerobic zone or an anoxic zone during operation; the zone B and the zone C can serve as aerobic zones and can also serve as anaerobic zones or anoxic zones during operation; the biological selection zone is arranged on the forepart of the reaction tank; the pre-anoxic zone is arranged behind the biological selection zone; the water distribution zone is arranged among the zone A, the zone B and the zone C; and the water outlet zone is arranged between the zone B and the zone C and is connected with the water distribution zone by the internal reflux channel. The nitrogen and phosphorus removal integrated biological reaction tank operating in multiple modes, which is provided by the invention, has the advantages that the biological reaction tank has the characteristics of intensification, small floor area and small quantity of equipment and can alternately operate in multiple modes; and the modes are switched freely and flexibly, so that impact load resistance is ensured and efficient biological nitrogen and phosphorus removal can be achieved under the condition that the inflow water quality changes more substantially.