The invention relates to new energy utilization, and the windmill generator in the invention comprises one or a plurality of main reducing nozzles which can rotate around a vertical main shaft or Laval nozzles, an exhaust device, an exhaust pipeline, one or a plurality of auxiliary reducing nozzles which are vertically and fixedly arranged or Laval nozzles and the like. One or a plurality of main wind mills are arranged in a cylinder which is provided with a rotary outlet of the main reducing nozzle or the Laval nozzle and an exhaust outlet. The exhaust device is used for lowering and controlling the outlet back pressure of the main reducing nozzle or the Laval nozzle so as to lead air current to acceleratly flow in the main reducing nozzle or the Laval nozzle and an air outlet to obtain ideal high wind speed. The exhausted gas is transmitted into the inlet of the reducing nozzle or the Laval nozzle in which the air inlet exactly points to the direction wind coming from through the exhaust pipeline to enhance the flow and pressure of the inlet of the reducing nozzle or the Laval nozzle, or dowork to generate electricity for the auxiliary reducing nozzles which are vertically fixed or the Laval nozzles.