Abstract: In order to improve the doubling frequency efficiency, the influence of beam waist position in frequency doubling crystal on the frequency doubling efficiency was analyzed. According to the propagation property of fundamental mode Gaussian beam, combining with the characteristic that equal phase plane of end mirror and cavity mirror having the same radius of curvature in the stable three-mirror-folded cavity, cavity mirror with the same radius of curvature was placed on the proper position and three-mirror-folded cavity with two Rayleigh length was realized. The efficiency of frequency doubling was improved. The stability regions of the cavity with one and two Rayleigh length were compared and the same stability regions were obtained. The experimental results show that when 5W fiber coupling 880nm laser diode is used to pump 3mm×3mm×5mm Nd:YVO₄ and quasi-phase matched PPMgOLN with dimension of 10mm×2.1mm×0.5mm is used as frequency doubling crystal, the overall conversion efficiency is improved about 18%. For the two types of cavity, beam quality is the same. The polarization direction of doubling frequency light is consistent with that of fundamental frequency light. Stable low noise green laser is obtained. The effectiveness of resonant cavity design is verified. The study is helpful to improve the efficiency of intracavity frequency doubling.