The wide applications of nanotubes in many fields including catalysis have attracted considerable interest. Herein, we designed a simple and facile synthesis route to synthesize sodium-doped g-C₃N₄ nanotubes (Na-CNTs), by means of the hydrothermal synthesis of intermediate and the subsequent treatment via microwave irradiation heating. This approach utilizes the self-assembly between melamine and cyanuric acid in the NaOH solution to form Na-doped melamine cyanaurate supramolecular intermediate. Then the supramolecular intermediate is heated under direct microwave irradiation with carbon fibers which are acted as microwave absorbents. The results of comprehensive characterizations indicate that Na-CNTs in the form of uniform one-dimensional (1D) nanotubes can be obtained conveniently, and the doping of sodium can be successfully realized by direct microwave irradiation heating. Moreover, sodium doping can enhance the charge attractive force between layers and induce more structural defects in Na-CNTs. The photodegradation result of rhodamine B (RhB) demonstrates that the as-obtained Na-CNTs exhibit enhanced photocatalytic performance, with a degradation rate of nearly 91.43 % in just 20 min, and the corresponding photodegradation velocity of Na-CNTs is 3.2 times higher than that of pure g-C₃N₄ (PCN).