Abstract: Aiming at the problems such as high pressurization ratio, wide suction range and multi-stage parameter matching in large hypersonic wind tunnel, this paper carried out the design calculation and suction test of the multi-stage ejector system in Φ1.2 m hypersonic wind tunnel. Through single stage performance debugging and multistage combination performance debugging of the first, second and third stage ejector without wind tunnel main flow, the suction performance of three stage multi nozzle central ejector with different working parameters is obtained. The minimum static pressure in the test section is 660 Pa without the main flow. And the parameter matching principle of efficient operation of the multi-stage ejector is analyzed and summarized. The test results of the ejector coefficient with the main airflow in the wind tunnel are in good agreement with the theoretical calculation values, which verifies the feasibility of the aerodynamic design method for the multistage multi-nozzle ejector. The design results are reliable, which can provide technical reference for the design of the multistage ejector system in the hypersonic wind tunnel or other ground aerodynamic test equipment.