The modeling,mesh division and calculation of the annular disc graphite seal leakage channel is difficult because of its small leakage channel size.A solution model of annular disc graphite seal leakage channel was proposed based on the similarity principle method.The similarity criterion of fluid flow in the annular graphite seal leakage channel was deduced by equation analysis method,and a mapping model following geometric similarity and dynamic similarity was obtained.The leakage channel mapping model was used to analyze the leakage flow characteristics of annular disc graphite seals,and the results were compared with the actual model calculation results.The results show that the similarity of gas flow in leakage channel can be characterized by Froude,Euler and Reynolds similarity criteria.The distribution of fluid pressure and velocity at the same structure position of the model before and after mapping has good consistency.The relative error between the leakage calculated by the mapping model and that calculated by the actual model is within the allowable error range,verifying the reliability of the deduced similarity criterion and mapping method for fluid flow in leakage channels.The research provides a new method to study the leakage flow characteristics of the small leakage channels in annular disc graphite seals.