The invention belongs to the technical field of water pumps, and particularly relates to a high-pressure injection pump. The high-pressure injection pump includes a rotor body, a collecting main, wherein the rotor body includes impellers and a rotor cavity, and the collecting main includes diffusion sections and an outlet pipe; the outer surfaces of the diffusion sections of the collecting main are in streamline shapes; and the diffusion sections of the collecting main are evenly distributed in an array mode in the circumferential direction of the outlet pipe, the number of the diffusion sections of the collecting main is at least 3, the outlet pipe of the collecting main is made of elastic materials, and the inner diameters of the cross sections of the outlet pipe are gradually decreasedfrom the left to the right. According to the high-pressure injection pump, the number of the diffusion sections of the collecting main is at least 3, thus water amount flowing into inner cavities of the diffusion sections is increased, rate of flow of water flowing into the outlet pipe and pressure of the water flowing into the outlet pipe are increased, the pressure and the rate of flow of the water flowing out of the outlet pipe are increased, the inner diameters of the cross sections of the outlet pipe are gradually decreased from the left to the right, thus when water flow passes the outlet pipe from the left to the right, water pressure is gradually increased, and thus the pressure of the water flowing out of the outlet pipe is increased.