Abstract:Based on the theory of transmission matrix,combining with Gaussian beam parameters,the influence of the varision of both the curvature radius of spherical mirror and the cavity length on the beam waist radius was studied in meridian plane and sagittal plane of the ring cavity.The results show that both the waist radius increase with the increase of the curvature radius and cavity length.It is also analyzed the influence of these changes on light intensity distribution,a variety of transverse modes coupling and equiphase surface size in ring cavity.