An ion beam etching system includes an etching cavity, an etching electrode, and an electrode displacement apparatus used for enabling the electrode to change a working position in the etching cavity. The electrode displacement apparatus includes a dynamic sealing mechanism, a dynamic electrode balance counterweight mechanism, an electrode displacement transmission mechanism, and an electrode displacement driving mechanism. The etching cavity includes a cavity and a cavity cover connected with the cavity. The cavity is of an irregular shape. The cavity includes a partial cylindrical body, a side plate, a tapered transition portion, and a bottom plate. The partial cylindrical body is laterally sealed by means of the side plate. The bottom plate is connected to an end of the partial cylindrical body by means of the tapered transition portion and seals the end of the partial cylindrical body.