The frequency stabilization of dye laser is described. The laser frequency is stabilized to the side of a transmision curve of an optical cavity by means of the usual differential servo technique. With a PZT cavity mirror driven by fast servo electronics and a galvoplate driven by slow servo electronics, the linewidth of the jet stream dye laser is reduced to 1 MHz. Experimental result is presented on the measurement of saturation spectroseopy of sodium D1 line.