The theory of dynamic gas lock (DGL) suppression ratio is systematically studied and the DGL theoretical model is provided. Then the suppression ratio formulas of DGL with uniform or variable sections are derived through theoretical calculation under the conditions of single- or multi-component purge gases. Moreover, the suppression ratios of uniform-section DGL and variable-section DGL are compared for single-component purge gas. The theoretical results show that the uniform-section supposition, taking the section area where purge gas flows out DGL as the average section area, can be used when the suppression ratio is more than 85%; the suppression ratio is related to the DGL structure and the parameters of purge gas, and the suppression ratio increases with the increase of the gas volume flux into the wafer chamber when the DGL structure and diffusion coefficient are constant. The theory system proposed on DGL suppression ratio can provide a theoretical basis for the development of DGL in the extreme ultraviolet (EUV) lithography.