We synthesized diamond via gaseous phase of vaporized acetone. Molecular acetone decomposes to two methyl radicals with thermal activation. We propose here a new method for diamond synthesis with these methyl radicals from molecular acetone. With this method, we successfully synthesized diamond particles on Si substrates with shorter experimental time and lower energy consumption than conventional methods. With liquid carbon sources, such as acetone, impurity elements will be easily substituted in synthesized diamond thin film, which has wide applications for the future electronic devices. Nickel, boron and phosphorus doping will be presented.