Multi-plating composite electroplating device for inner wall of oil pipe and electroplating method

The invention discloses a multi-plating composite electroplating device for an inner wall of an oil pipe. The device includes a liquid supply tank which is communicated with one end of the oil pipe and through which working liquid can be injected into the oil pipe; a liquid returning tank communicated with the other end of the oil pipe, with the working liquid passing through the oil pipe being discharged into the liquid returning tank; a circulating pump configured to circulate the working liquid among the liquid supply tank, the oil pipe and the liquid returning tank; one or more rotating mechanisms that drive the oil pipe to rotate in the axial direction; one or more oil pipe conductive mechanisms electrically connected to the oil pipe; positive electrode conductive mechanisms disposedon both sides of the oil pipe; and an auxiliary positive electrode capable of coaxially disposed in the oil pipe, with two ends of the auxiliary positive electrode being electrically connected to thepositive electrode conduct