The Earth’s asthenosphere may refer to the dynamic source of global tectonics, magmatism and mineralization. Although people have recognized the importance of the asthenosphere’s tectonic dynamic, magmatism and mineralization, there is little indepth study of its formation mechanism in specific and quantitative tools. In recent twenty years, a series of research results in the radius change of the Earth show that the expansion of the Earth has much direct evidence. Accordingly, even calculated by inflation rate (0.1 mm/a) of the radius of the late Earth expansion, the result of the Earth expansion will also be a global super tectonic event. According to the nonlinear limited expansion evolution of the Earth, the asthenosphere cause model is that, the expansion internal pressure from the original deep Earth pushes the top of the primitive mantle acting and is converted into compression energy A acting on the top mantle material under confined by original lithosphere shell. When the accumulating compression energy exceeded the thermal energy Ω required to melt the part of material on top original mantle, the uppermost mantle material began to melt and gradually formed the Earth’s primitive asthenosphere. Accordingly, assuming that the radial growth rate of nonlinear limited expansion at the beginning expansion period of the Earth is 1.08 mm/a, the meltdown rate of the top material of primitive mantle is 15%, under the condition of adiabatic isobaric process, it will only need 19.2 Ma to form the Earth’s original asthenosphere after the Earth began to expand.