The invention discloses a preparation method of tungsten-cladding-copper nanometer composite powder with controllable thickness of a cladding coating. The method comprises the following steps of: uniformly mixing CuO powder with the mass of m1 with WO3 powder with the mass of m2; placing the mixed powder in a furnace for sintering; adding ground CuWO4 powder into CuO powder with the mass of m3, mixing, and placing the mixture into a hydrogen reduction furnace; introducing hydrogen into the furnace with the introduction rate of 33L/min; raising the temperature to 360 DEG C with the temperature raising speed of 5-10 DEG C/min, keeping the temperature for 10min, raising the temperature to 800 DEG C with the temperature raising speed of 3-5 DEG C/min, and keeping the temperature for 30 min; stopping introducing hydrogen, introducing helium with the speed of 20L/min, cooling along with the furnace to room temperature, and stopping introducing helium to obtain the tungsten-cladding-copper nanometer composite powder. By adopting the preparation process, the thickness of the tungsten cladding coating can be precisely controlled in the nanometer order of magnitude, thereby the application requirements of different tungsten and copper proportion contents can be satisfied.