In view of the application requirements of electric propulsion system for China’s asteroid deep space exploration mission, the overall scheme is designed, an ion thruster prototype model is established by using a four-ring-cusp field discharge chamber, 30-cm beam current extraction diameter three-grid ion optics system. Reasonableness and compatibility of discharge chamber and grid design are verified experimentally and theoretically . The test results are shown below. The ion thruster can operate steadily over an input power envelope of 277–3120 W, thrust increases linearly from 9.9 to 117.2 mN, specific impulse rises from 1269 to 3492 s, the beam divergence angle drops from 30.7° to 26.8° and stabilizes above a certain power value, the thrust vector angle is less than 1.5° and beam flatness parameter is greater than 0.75 at different operating points. The maximum percentage reduction in grid gap aberration is 90% with the strain relief molybdenum mounting ring thermal design. This research provides a reference for multi-mode ion thruster design and in-orbit engineering applications.