Abstract: Baffle aperture architecture is a vital factor for ion thruster which uses the divergence magnetic field topology.And energy and velocity distribution of primary electron injected into discharge chamber are heavily influenced by the aperture size.Setting cathode baffle could effectively improve beam distributions of the ion optics system，and the working stability of the ion thrusters with long life.In the paper，Brophy introduces the process of deducing the principle of the plasma model near the divergent ion thruster baffle channel，and the distribution of plasma parameters of the channel of kafman-type ion thruster through experiments by Milligan.Through the use of Langmuir probe measurement technique，the distribution of plasma parameters near the baffle channel is obtained，which plays a theoretical guiding role in the distribution of the plasma parameters of the ion thruster baffle channel in the future.