Hydraulic pulse supercharging underbalance drilling unit

The invention relates to a hydraulic pulse supercharging underbalance drilling unit comprising a body with two oblique flow passages, an impeller, a base, an impeller shaft and the like. The base is mounted in the body through positioning pins, and two effusion passages are symmetric to a plane of the two oblique flow passages on the body. The impeller is mounted above the base through the impeller shaft. A basic operating principle includes that drilling fluid passes an inner cavity of the device body to drive the impeller to rotate, baffles under the impeller can periodically open and close the effusion passages of the base so as to change sectional area of fluid passing, the continuous drilling fluid flowing through the device is modulated into a pulse form, and accordingly rock clearing efficiency is improved; when the effusion passages are opened and closed periodically, lateral openings of the impeller can correspondingly close and open the oblique flow passages to enable the drilling fluid to be ejecte