The invention discloses a full-order terminal sliding mode control method based on a back-to-back VSC-HVDC. The two converters are controlled in the same way. The inner loop controller of the converter uses a full-order terminal sliding mode controller. The outer loop controller of the converter uses a PI controller. The outer loop controller outputs a reference current to be inputted to the innerloop controller. The inner loop controller outputs a voltage signal through the full-order terminal sliding mode controller and outputs a modulation signal through modulation to control on/off of theconverter. According to the inner loop and outer loop PI controller based on the full-order TSM, the cross-coupling term of the current in the two-phase static reference system can be avoided. The controller does not require feedforward decoupling so that the whole control system is enabled to be simple.