A design method of system parameters of unstable ring resonators with 90° beam rotation is discussed in this paper, and an effective method of allgment of the resonator is also gaven. Good output far-field intensity distributions of the UR90 resonator with the magnification M=1.21 and 1.3 are observed in the copper vapor laser. The reverse mode is successfully suppressed on the UR90 resonator while the polarization state of the reverse mode remains by a reinjection system.