In order to attain optimal sum-frequency 593 nm yellow laser, using LD end-pumped Nd:YVO4, starting from the four-level system rate equations, a theoretical model of the spatial related dual-wavelength rate-equation was established and dual-wavelength photon number expression was conducted. The parameters of the three-mirror compound resonator were theoretically obtained for the LD end-pumped Nd:YVO4／KTP yellow laser with sum-frequency in the case of equal dual-wavelength photon number density. The output power of 593 nm yellow laser was experimentally compared under the conditions that dual-wavelength laser photon number density was equal and the dual-wavelength laser oscillation threshold was equal. Output power of 593 nm yellow laser was respectively 410 mW and 340 mW, and the conversion efficiency was 3.4% and 2.8% in the two cases with 12 W pump power. The experimental results show that more efficiency yellow laser can be obtained in the case of equal dual-wavelength photon number density.