A parallel-plane cavity Fabry-Perot interferometer is designed and made to narrow the linewidth of the pulsed dye laser from 4 GHz to 340 MHz. The Fabry-Perot etalon photographing method is used to monitor the laser line type in real time, and the synchronous scanning of the pulse laser line type is realized. With the iodine absorption spectrum measurement, we built a fine-wavelength tuning and calibration system on the 100 MHz scale of the linewidth narrow pulsed dye laser. The laser system is used in the laser-induced fluorescence diagnostic of oxide-coated cathode discharge argon plasma. The feasibility of the linewidth narrowing system is verified, and the velocity resolution of the ion velocity distribution function is up to 200 m/s.