To investigate different effects of anaerobic modes on recovery of partial nitrification (PN), two-stage continuous stirred-tank reactors (CSTR)1# and 2# were used at room temperature (20±2) ℃. The experiment had three stages (S1, S2 and S3). During S1, 1# was maintained anaerobic / anaerobic (DO: 0-0. 1, 0-0. 1 mg / L), 2# was maintained anaerobic / oxic (DO: 0-0. 1, 0. 6-0. 8 mg / L). During S2, 1# was maintained oxic / oxic (DO: 0. 2-0. 4, 0. 6-0. 8 mg / L), 2# was continually maintained anaerobic / oxic (DO: 0-0. 1, 0. 6-0. 8 mg / L). To investigate stability of PN after recovery, S3 was carried out. During S3, 1# and 2# was maintained oxic / oxic (DO: 1. 0-1. 2, 1. 0-1. 2 mg / L) The following paremeters (time of recovery of PN and stability of PN) were investigated. It demonstrated that the recovery time of 1# was shorter than that of 2# by 12 d. However, PN in 2# was more stable when DO increased to 1. 0-1. 2 mg / L. Efficient PN could be recovered by the mode of first anaerobic / anaerobic (DO: 0-0. 1, 0-0. 1 mg / L) then oxic / oxic (DO: 0. 2-0. 4, 0. 6-0. 8 mg / L). Afterwards, stable PN could be maintained by anaerobic / oxic (DO: 0-0. 1, 0. 6-0. 8 mg / L).