Combustion flame method in diamond microcrystal-line film formation has attracted much attention because it demonstrates highly practical growth rates (~µm/min), which is an order of magnitude greater than that of conventional chemical vapor deposition methods, as well as its feasibility as a process conducted under atmospheric ambient. In this article, various techniques developed by the authors for this method have been reviewed. They include the use of a preformed oxide film on the molybdenum substrate, the simultaneous application of a magnetic field, the inert-gas curtain method, the combustion-flame current measurement to monitor the growth, and the growth enhancement by the multi-stepped negative biasing. The success of these methods in turn gives us insights into the growth mechanism of the diamonds, such as the clarification of the role of the outer flame or the notice on the presence of the optimum radical density for the diamond growth. Further improvements in our under standings may add more developments in this promising method for the diamond growth.