Belonging to the technical field of thermal conductive interface materials, the invention relates to a low viscosity and high thermal conductivity organosilicon gel and a preparation method thereof. The low viscosity and high thermal conductivity organosilicon gel consists of a component A and a component B. Specifically, the component A comprises the following components: vinyl silicone oil, polyvinyl silicone oil, alkyl modified silicone oil, an active diluent, high thermal conductivity compound inorganic filler, a catalyst and pigment; and the component B comprises the following componentsby mass: vinyl silicone oil, polyvinyl silicone oil, alkyl modified silicone oil, an active diluent, high thermal conductivity compound inorganic filler, hydrogen-containing silicone oil, an inhibitorand a tackifier. The product provided by the invention has the characteristics of low viscosity, high extrudability and high thixotropy, and easy mixing, can be compressed into filling layers of different thicknesses and different shapes, can be quickly solidified into soft silicone gel at normal temperature and by heating, is suitable for filling the irregular gaps among various electronic devices and heat dissipators, and can play the role of heat conduction, insulation, buffering, shock absorption, etc.