Abstract: Microwave plasma chemical vapor deposition（MWPCVD）is an important method for preparing diamond films. The reaction chamber-water-cooled MWPCVD apparatus for high rate and large-area deposition of diamond films has been successfully developed.It can steadily operate for a long time under the condition of 3.0 kW input microwave power.The diamond films have been successfully prepared on silicon substrates with this apparatus.