Abstract: A DC arc plasma jet apparatus was established to prepare diamond film with good quality. High deposition rate of 65 μm/h was achieved on non-polished molybdenum substrate, and diamond films can be deposited in an area as large as 10-20mm in diameter. The diamond films were analyzed by Raman spectrum and SEM. Raman results showed only a peak at 1334cm-1, which fitted well with that of natural diamond. SEM results showed that diamond crystal grew well and the film was dense and uniform. Several forms of diamond crystal in our research were presented. Finally, a preliminary discussion on the formation of diamond film was made.