Abstract: Grid system is the key assembly of ion thruster，whose main function is to extract and accelerate ion to generate thrust.However，grid's geometry is the dominating factor for performance and stability.This paper elaborates the study of grids shape related to heat treatment temperature，duration and operation procedure based on molybdenum heat treatment process under hydrogen circumstance，and finds out the proper molybdenum grid heat treatment method and technical parameters.The heat treatment results of 30 cm molybdenum grids show that the method and technical parameters are suitable for grid treatment，the grid profile deviation is under 0.1 mm，while gird gap tolerance is controlled within 0.1 mm which improves performance and reliability of grid assembly.