Because of the particularity of low-permeability gas reservoir, the traditional methods to calculate the dynamic reserves, such as pressure drawdown method and elastic 2-phase method, don’t fit to the low-permeability gas reservoir properly, or need harsh requirements, Which is hard to use. This article presents a new method to calculate dynamic reserves of low-permeability gas reservoir, which is so-called rate transient method. Basing on the combination of material balance equation and pseudo-steady flow equation, the method can be used to calculate dynamic reserves only taking advantage of the daily production data (rate, tubing pressure and casing pressure). The article also presents the applied example, and the comprehensive analysis shows that the new rate transient method is better than the traditional methods for calculating dynamic reserves of low-permeability gas reservoir.