Preparation of high quality graphene with uniform layers currently remains a bottleneck. In particular, graphene with only one large-sized monolayer is very difficult to obtain. With epitaxial growth of graphene under a hydrogen atmosphere and high temperature, even as high as 1550 degrees C, the obtained graphene was intercalated by methane and methyl group (-CH(3)) species. Spontaneously, this intercalation makes the coupling of adjacent layers weak and leads to each layer behaving like free-standing graphene. X-ray diffraction spectra demonstrate that the interdistance of adjacent layers is abnormally large, disclosing each layer suspended by the intercalation, regardless of the layer number. Our findings have opened a possible route to prepare free-standing, high quality graphene effectively in large-scale, behaving like one monolayer free-standing graphene. The Raman spectra also support this conclusion.