A multi-stage sewage treatment method with biological denitrification and dephosphorization is provided, which comprises the following steps of : introducing the sewage into an anaerobic pond (110), introducing the sewage treated in the anaerobic pond (110) into an anoxic pond (131) at the front section of an anoxic-aerobic treatment unit (140), introducing all sewage through a last stage aerobic pond (132), then discharging it into a settling pond, draining the settled sludge into a returned sludge concentration pond (170), draining supernatant in the returned sludge concentration pond (170) into the last stage aerobic pond (132), and draining the sludge in the returned sludge concentration pond (170) into a pre-anoxic pond (190) then into the initial anaerobic pond (110) for circular treatment. Simultaneously, a multi-stage sewage treatment device with biological denitrification and dephosphorization is also provided. The method has the advantages of only adding the returned sludge concentration pond (170) and the pre-anoxic pond (190) compared with the A2O process in the prior art and improving reaction efficiency by adjusting the connection relationship among the reaction ponds.
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