The invention discloses a method for preparing a tungsten coating through molten salt in-situ electro-deposition, which comprises the following steps: under the protection of inert gas, by using a tungstate system containing rare metal oxide as molten salt electrolyte, metal tungsten or tungsten-based alloy as an auxiliary electrode and a conductive electroplated part as a working electrode, heating to melt the molten salt electrolyte, keeping the temperature, and carrying out in-situ electro-deposition, thereby obtaining the tungsten coating. The rare metal oxide is one of rare earth metal oxide and zirconium oxide. The rare metal oxide is added into the tungstate system, so that the tungsten coating prepared through in-situ electro-deposition is compact in structure, smaller in grain size, higher in bonding strength, high in hardness and better in wear resistance; compared with the prior art, the tungsten coating with better flatness can be prepared without subsequent processing treatment, and the thermal shock resistance is more excellent; the method disclosed by the invention has the characteristics of high efficiency, greenness, short flow and controllable product, and is simple in process equipment, convenient to operate, low in cost and wide in actual application prospect.