Abstract: On the 10 kWmicrowave plasma chemical vapor deposition device independently developed by the laboratory,the influence of the gas flow mode on the uniformity and quality of the diamond film were discussed by changing the way of gasin and out.The resultsshow thatwith the increase of the number of gasmoleculeson the surface of the Sisubstrate,the strength of the H atoms and CH active groups in the plasma increases,and the number of atoms H and carbon-containing active groups diffused to the center of the substrate surface increases.The growth rate of the diamond film was slightly increased,from 2.5 μm/h to 2.8 μm/h,and the quality and uniformity of the diamond film deposited were improved.