In order to further understand the frequency of Helmholtz pulse combustor, a Helmholtz type combustor was used to carry out the experiments in conditions of different gas flow rates. Through the experiments of three lengths tail pipe, frequency was all increased while the gas flow rate increased. The impact of gas flow rate on frequency was investigated, and the modification of theoretic formula was also proposed based on the difference between the theoretical and actual values. Compared with the experimental values, the results showed that the predicted values and the experimental values matched well.