Abstract: By using a tractable plasma description, distribution of microwave plasma under various operating conditions for deposition of diamond films in a cylindrical microwave plasma reactor has been simulated. In simulation, for the growth environment of nano-diamond, dependence of plasma distribution in the rector on the microwave input power and gas pressure of pure argon atmosphere has been studied. The simulation results were compared with the corresponding results of hydrogen atmosphere. The results obtained will be of help in effort to optimize operating conditions for the deposition of diamond films.