Stilbene 420 dye solution was prepared and the laser dye absorption spectrum was measured. Q-switched frequency-doubling Nd∶YAG laser was used as the pumping source to realize the stilbene 420 dye laser and fluorescence spectra analysis. Laser spectroscopy reached the strongest peak at 425 nm and full width at half maximun (FWHM) is 1 nm. Spectral range was from 420 nm to 440 nm. Fluorescence spectrum peak was at 428.5 nm. Compared with the strongest peak laser, the wavelength difference was 3.5 nm. The highest dye conversion efficiency was 9.26%.