Abstract: In the area from Beijing to Chengde the extensive occurrences of the Archaean-Proterozoic crystalline rocks are composed mainly of two suits of metamorphic rock series; the Miyun Group in the lower member dominated by hypersthene-granulite and hornblende-granulite, being the type of orthogneisses and named "gneiss series" in the past: the Zhangjiafeng Group (or Huairou Group) in the upper member in predominance of crystalline schist, belonging to the paragneisses, and which used to be referred to as "crystalline schist series".In this paper the earth’s origin was presumed by virtue of the above-mentioned metamorphic rocks. It is assumed that the original earth may stem from the nebula. Originally the earth would have a layer of " a basic "scoria shell" after it had formed. And this may be the initial embryonic crust of igneous rocks. Because of its outer crust the transmission of heat was difficult, and then the rock differentiation of the inner crust took place, leading to the generation of the magmatic source in the upper crust.Geothermal and magmatic sources having an effect on the scoria shell would cause metamorphisms and then form the crust of basic orthogneiss, the lower crystallized crust.At that time the wavelike folding deformation due to the contraction happened over the crust. However, the deep-seated faults would never occur within the crust. Consequently, a large scale of intrusion and eruption of the magma was of little possibility and only the dissemination and injection of the magma appeared in dispersion form, leading to a general migmatization. The temperature of the ground surface had since decreased rapidly and the solid crust was under the action of the internal and external stresses deformed and fractured to cause uplifts and depressions, and followed by the erosion and sedimentation. The consolidated sedimentary rocks were accompanied by the magmatic activity and the metamorphism to form the paragneisses. i. e. the upper crystalized crust.On the basis of the composition and occurrences of the ancient rocks together with the characteristics of metamorphism, magmatism and tectonic movements, the earth’s origin discussed in this paper may be assumed to be a general rule for the accretion and evolution of the earth.