Platinum was deposited onto molybdenum grid by ion beam assisted deposition (IBAD). Electron emission behavior from molybdenum grids with and without Platinum contaminated by active electron emission substances (Ba, BaO) of the cathode were measured using analogous diode method. The characteristics on molybdenum grid coated with platinum film were analyzed by X-ray diffraction (XRD), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The results show that the electron emission from the grid coated with platinum film is less than that without Platinum film, and the mechanism for suppression of the electron emission of molybdenum grid coated with Platinum film was discussed.