The Mn-N codoped ZnO thin films are fabricated on quartz glass substrates using the radio-frequency magnetron sputtering technique together with the direct N+ ion-implantation. The effects of annealing temperature on microstructure and room-temperature ferromagnetism of the thin films are investigated. The results indicate that both divalent Mn2+ and trivalent N3- ions are incorporated into ZnO lattice. As the annealing temperature increases, the lattice distortion induced by N+ ion-implantation can decrease, and the N3- may escape from the film, which results in the reducing of acceptor (NO) concentration. Ferromagnetism is observed in the (Mn,N)-codoped ZnO thin film at 300 K and found to be the sensitive to the acceptor concentration. The mechanism of room-temperature ferromagnetism in the ZnO:(Mn, N) is discussed based on the bound magnetic polaron model.