Experimental setup and experimental results of an ultrashort cavity Rh-B dye laser pumped by frequency-doubled pulses from a mode-locked Nd phosphate glass laser are reported. The optimum operation conditions of the mode-locked Nd phosphate glass laser were studied by a combination equipment of TPF and OSA. A pulse train with pulse width of about 5 ps was’obtained. Using this picosecond laser as pumping source, an ultrashort cavity dye laser with tunable monomode pulses of less than 4ps and wavelengths ranging from 620.1 am to 641. 6nm was obtained.