Abstract: Most outcropped Archean rocks(such as TTG, komatiite and greenstone belt) are different from the modern ones.Therefore, the idea of "the present is the key to the past" is not suitable to be extended to the Archean Eon, nor can the Archean TTG be compared to the present adakites.TTG had nothing to do with subduction, and might be formed by partial melting of sodium-rich basalts in the initial crust under the tectonic setting of the stagnant lid instead of by crustal thickening.The earth is a process of continuous heat dissipation.The Archean Eon belongs to the hot sphere stage, and the earth might enter the cold sphere stage after the Proterozoic Eon.Therefore, the Archean might be mainly characterized by stagnant lid tectonics, and plate tectonics might have appeared after the Proterozoic.As possibility of plate thermal subduction is small, only when the lithosphere is cold enough and has certain rigidity and buoyancy, can the plate subduction occur.Only by establishing the geological record of plate tectonics(such as ophiolite, blueschist, melanges, deep-sea deposits, etc.) can we know when plate tectonics began.