In physics,the energy conservation and least action principle are of universal effectiveness.Fermat proposed that the ray of light has the least time for path traverse through different media based on the proof by simple geometry.In social structure people will choose different understanding and reaction to a same event depending on their states.How can people choose the least resistance approved by behavior from different states,different classes and different layers (equalevant to different media) may be considered as the attempt of applying the Fermat’s principle of least action to find the social optimal organization.That is also an important content for explaining social phenomena and giving the universal answer by sociophysics.Based on the fundamental thinking of least action principle,the paper tries to find the existence of least action in every layer of society,furthermore to link the global optimization of n layers in society,and thus to find the exact analysis of the theory of social optimal management in some extents.