Being different from classic dimension analysis method and dimensionless method of flow's governing equations and its certain resolving conditions, this paper presents a new method to analyze flow's similitude law, scilicet decomposing complicated flow process to some sub-processes and analyzing characteristic quantity which represents sub-process' essence nature. According to this new method this paper presents law of similitude in non-equilibrium thermo-chemistry hypersonic flows, which is consistent with the law of similitude obtained by classic method in reference.