Abstract: With the microwave plasma chemical vapor deposition (MPCVD) the effects of methane concentration deposition pressure and gas flow rate on diamond coating on single crystal silicon substrate were studied systemically.The SEM pictures of different samples showed that the above mentioned parameters had very important influenced about the micro-pattern of diamond films,such as the size of crystal particle,steadiness,continuity,compactness,etc.The sharp peak 1 332cm-1 of diamond films' Raman spectrum showed that the films had good crystallization quality,it had the same result with the SEMpicture.Finally,its properties of field emission were studied,the emission can be obtained at field as low as 4.4V/μm, and the high emission current density about 128 mA/cm2 was got at 650 V.