It was studied that the MPI spectra and the TOF mass spectra of tetramethylsilane with parallel plate vacuum cell and supersonic molecular beam system with UV laser radiation in the wavelength range of 383 to 373 nm. In experiments, seven strong peaks of MPI spectra were gumed but only three were assigned to (2+1) ionization of Si atoms. TOF mass spectra showed that Si+ and constantly appeared.A general conclusion was gumed that the MPI machanism of tetramethylsilane was class B photochemical process.