Abstract: Baffle aperture architecture is a vital factor for ion thruster which uses the divergence magnetic field topology.And the energy and velocity distribution of primary electron injected into discharge chamber are heavily influenced by the aperture size，and then the performance of discharge chamber is affected.According to the plasma characteristic in the baffle aperture，this paper establishes a calculation model of baffle aperture geometry design which relies on ion thruster discharge parameter.Using this model a geometric value of baffle aperture is calculated in 10 cm ion thruster，and three different feature sizes are designed near this calculated value，and the feature sizes are also optimized by the tests.Ultimately，the optimized baffle aperture size is applied in 10 cm prototype ion thruster.The test result shows that the performance of the ion thruster satisfies the design requirements，and also verifies the rationality of the baffle aperture design model in 10 cm ion thruster.