A high-repetition pulsed Nd  :  YVO₄ laser based on the multi-longitudinal-mode beat note is presented. The mechanism of multi-mode oscillating in the Nd  :  YVO₄ laser with FP cavity is analyzed. With the multi-mode Nd  :  YVO₄ laser in experiments, it is found that the more longitudinal modes beating in the laser cavity, the narrower time duration of the laser pulse is obtained. An adjustable aperture is employed in the laser cavity to weaken the transverse mode interference and improve the laser pulse train stability. At last, when the FP laser cavity length is 88 mm, by slight tuning the Nd  :  YVO₄ crystal temperature, a 1.56 GHz high-repetition laser pulse with 0.18-ns time duration is achieved. The average output power of the pulse train is 1605 mW with the pump power at 6788 mW. The slope efficiency and the optical-to-optical efficiency are calculated as 31% and 24%, respectively.