The third harmonic of Nd-YAG- laser has been obtained by frequency summing with a peak output power of about 1.7MW is used to pump a dye laser, and the wavelength tuning range is from 409.3 nm to 682.3 nm. A peak power of more than 0.60 MW is generated at 450.0 nm, the center wavelength of eoumarin 47. When coumarin 152 is used alone, a broad tuning range of up to 104.2 nm has been obtained, which is close to its fluorescence linewidth of 120.0 nm.