Abstract: For reasonable advice to 30 cm diameter ion thruster's thermal design, the thermal behaviour of a LIPS-300 ion thruster is described by finite element analysis software. Steady-state temperature distributions and thermal deformation for the thruster are simulated. The Steady-state thermal analysis results show the high temperature components are taper discharge chamber, upstream cylindrical and downstream harness. The thermal deformation analysis results exhibit discharge chamber and outer shell deformation is the chief influence factor. The simulation results suggest that increase emissivity and reduce absorptivity of thruster components will reduce the temperature distribution effectively.