A hydraulic automatically-pressurizing pump comprises an intermediate fastening connector, a reversing valve, a mechanically-controlled automatic direction-reversing device, a power cylinder, a pressurizing cylinder and an ultrahigh-pressure connecting tube which are disposed in series in a case and assembled from the upper end to the lower end along a central axes of the case. The fastening connector is connected with the case and further connected through pressure with the reversing valve. The power cylinder is a multi-stage power cylinder. The pressurizing cylinder communicates with a two-channel drill bit through the ultrahigh-pressure connecting tube, and an ultrahigh-pressure channel is provided on the wall of the pressurizing cylinder. The core of the reversing valve is connected with the mechanically-controlled automatic direction-reversing device. The present invention is suitable for a pressurizing pump for large-discharge drilling wells, which can efficiently increase the drilling speed, reduce the cost for the whole machine.