The effect of multi transversal mode on quadrature frequency conversion in a solid-state laser was analyzed, and the relation between the conversion efficiency and the divergent angle was conducted. A quadrature frequency conversion scheme using two KTP crystals was implemented in an all-solid-state Nd∶YAG laser with high-order transverse mode. An energy-conversion efficiency of 75.5% is obtained when the fundamental laser intensity is 121 MW/cm2. This experiment indicates that when the parameters of nonlinear crystals are properly optimized, high-efficiency frequency doubling can be achieved using quadrature frequency-conversion scheme even in a multimode solid-state laser.