Abstract: Grid of an ion thruster is thin wall with multiple apertures and main function is to extract and accelerate ion to generate thrust. In order to reinforce the stability and strength of grid system,especially for large grid system,the shape usually is made into sphere like. Moreover,the system must be able to go through a series of severe vibration and impact test. Hence the material mechanical property is vital. This paper depicts the study of mechanical properties of gird material. The experiments tested several annealing temperature and duration combinations for molybdenum,and obtained strength and ductility by tensile tests. By combining metallography analysis,annealing parameters were selected for the heat treatment of molybdenum grids.