The field electron emission characteristics of nanocrystallinediamond films and discontinuous diamond films deposited on poroussilicon substrates with MWPCVD technique were investigated mainly.On the one hand, there was a lot of defects on the surface of poroussilicon prepared by electrochemical etching. When diamond wasdeposited on the porous silicon substrates, the high nucleation densitywas obtained and the adhesion between the diamond and the substratewas improved. On the other hand, enlightened by standard lithography,diamond protuberance quasi-arrays were deposited on the poroussilicon when regarding it as matrix. This was a cheap and efficientmethod for a fine field emission. Before the deposition of diamondfilms on the porous silicon substrates, their photoluminescence wereexamined. The photoluminescence characteristic of porous siliconprepared under condition that the current density was 20mA/cm2 andanodization time was 15 minutes was measured. It was found that theporous silicon luminesce visible light around 750nm wavelength underthe room temperature. The morphology of the porous silicon wasobserved with SEM. The observation shown that the pores size of theporous silicon was about 1μm and uniformity, its porosity was higher.The diamond film was deposited on the porous silicon.