The cavitation characteristics of the vertical water-injection at different initial velocities of streamlined and flat head low-speed cylinders are tested, and the water entering process is photographed with a high-speed camera. The effects of the initial velocity and head shape on the cavity morphology and motion characteristics of the cylinder into the water are discussed. The results show that：with the increase of water-entry speed, the closed length of the cavity is increased； the collapse velocity of the tail cavity is accelerated, and the closed jet of the tail is intensified, resulting in the increase of the bubble of the splashing crown, and the height and width of the reflected water column caused by the collapse；the speed at which the cylinder reaches a uniform speed and the time required for cavity closure are increased；the streamlined cylinder produces smaller cavitation and less cavity collapse time; the speed of the streamlined cylinder to achieve uniform motion is significantly greater than that of the flat cylinder, but it takes longer time to reach uniform motion.