Abstract: A method for wastewater treatment in a bioreactor, comprises recycling organic sludge in the bioreactor to supply carbon sources for removing nitrogen and phosphor and increase organic loading of the reactor, and adjusting operational parameters for the bioreactor to form facultative-anaerobic environment or anaerobic environment in the bioreactor. By following the method of the present invention, recycling sludge and simultaneously removing nitrogen and phosphor are completed such that the treatment processes for wastewater disposal are simplified; the sludge is recycled as carbon sources in the bioreactor such that saving resources is realized and the carbon emission into atmosphere is reduced; and zero-amount sludge is discharged such that harm from secondary pollution is avoided.