The invention relates to an inner throttling device of a heat exchanger. Most current production system throttling orifices are arranged outside the heat exchanger, and therefore a large portion of pipelines of the bypass of the heat exchanger are wasted, systems are complexly arranged and cannot be maintained easily, and the budge expenditure is increased. The inner throttling device comprises a throttling orifice (1) which is connected with a pass partition plate (2) through a bolt (3), a nut (4) and a retreat stopping gasket (5) to form the integral throttling device. The pass partition plate (2) is welded inside a heating exchanging pipe box (6). The throttling orifice is fixed on the pass partition plate through a bolt, and due to the fact that the pass partition plate is welded inside the pipe box, the purpose of controlling the flow of heat exchanging pipe media flowing through the heat exchanger according to the proportion is achieved. The inner throttling device of the heat exchanger is suitable for throttling devices inside heat exchangers.