Taking Wuhan Metropolitan Area as an example, this paper builds a series of accessibility analysis variables to reveal the spatial-temporal evolutional laws of accessibility of the road network at county level The spatial distribution of road network accessibility, which represented the symmetry establishing or breaking of Natural-Human Geography, is actually resulted from the "carving" of Natural Geographical pattern and the driving of the distribution of Economic Geography, it's also the spatial response of synergistic effect between self-organization and hetero-organization of Natural-Human Geography System, showing the unity of opposites on proportionality-centralization, stability-dynamic, deterministic-randomness, symmetry establishing-breaking. Therefore, this paper interprets the spatial symmetry principle of the county accessibility of Wuhan Metropolitan Area based on the action mechanism of Natural-Human Systems. Generally speaking,although the boundary contour and surface morphology of Wuhan Metropolitan Area is an irregular body,some kind of symmetry order under the action of the man-land relationship is hidden behind that, this order not only showed the symmetry of node location distribution, also showed the symmetry of node intrinsic attributes.