Analysis on interior fluid field of the air-driving reverse circulation bit was based on the experiment for a long time. With the development of the computer, amount of the numerical simulation and emulation software brought more advantages than the experiments. However, due to the complexity of the interior fluid field, few people could make resolution calculation for it. In this article, by simplifying the interior fluid field character of air reverse circulation bit, the air dynamics and fluid mechanics was used to calculate the air distribution in the bit; and the flow distribution equations were obtained. It can be shown that the simultaneous equations have a unique resolution. The article will provide the help to effectively make certain that the parameters of the bit structure and deeply study the interior fluid field character of air reverse circulation bit.