An integrated theoretical analytic platform is developed, which consisted of the thermodynamic model, beam transformation model, energy transition model and active unstable resonator model. The main conclusion of theory analysis is that: the beam-quality and optical-optical efficiency are weakly impacted by the length of resonator on fixed gain; the optimal efficiency and beam-quality are different corresponding to magnification for unstable resonator. The experiment of phase plate with passive resonator compensation is accomplished, the beam quality is improved from 5.48 times of diffraction limit to 2.46, with the output power of 12.1 kW.