Abstract: By using the side-pumped Nd∶GdVO4 crystal and type-I critically phase-matched LiB3O5 (LBO) crystal in cavity, the red light at 671nm was obtained. The cavity type of plane-concave was used to avoid decreasing the efficiency of doubling frequency caused by astigmatism. The parameters such as the resonant cavity curvature radius, length and laying position of crystal were optimized by software. The 671 nm red light of 9.7 W was obtained with injected electric power of 750 W. The repetition rate was 10 kHz, the angle of divergence was 7.9 mrad, and the electric-optical conversion efficiency was about 1.3%.