The invention discloses a full-transition metal nitride current collector/electrode supercapacitor and a preparation method thereof, and belongs to the technical field of new energy materials and devices. Firstly, impurities on the surface of a substrate material are removed through cleaning. Secondly, a layer of high-density and high-conductivity transition metal nitride film is deposited on thesurface of the substrate to serve as an electron transport current collector material. Thirdly, a layer of loose, porous and low-conductivity transition metal nitride film is directly and continuouslygrown on the current collector by regulating and controlling deposition process parameters to serve as an electrode material. According to the invention, the current collector and the electrode are both transition metal nitrides which grow continuously. The performance of the material is cut by simply changing film deposition process parameters. The preparation method is simple, convenient and feasible in process, low in cost, multiple in thin film deposition technology selection types and high in process applicability. The problems of layered cracking and large contact resistance caused by poor adhesion force, lattice mismatch and thermal expansion coefficient difference between a heterogeneous current collector and an electrode material are solved. The power density, the thermal stability and the long-term service reliability of the super capacitor are greatly improved.