Abstract: A new space transportation protocol identification algorithm based on multilevel template analysis is proposed by combining the distance judge algorithm and template analysis idea.The first level template can be built by space protocol characteristics,the second level template can be built by the distances between the first level templates.Then,the distance judge algorithm is used to make the template analysis and realize protocol identification.Experiment results demonstrate that multilevel template analysis improves the efficiency of space protocol identification and provides new ideas for the research of protocol identification techniques.