g-C₃N₄/g-C₃N₄ homojunction（CN-HP） with the morphology of porous nanosheets and hollow nanotubes was pre-pared from supramolecular precursor prepared by mixed calcination of dicyanodiamine hydrothermal method and melamine-cyanuric acid coprecipitation method.The photocatalyst was characterized by X-ray diffraction（XRD）,scanning electron mi-croscopy（SEM）,transmission electron microscopy（TEM）,ultraviolet-visible diffuse reflectance（UV-Vis DRS）,photolumi-nescence spectroscopy（PL）,etc.The results showed that CN-HP-1/1 exhibited a degradation rate of 99.8% for methylene blue（MB） within 75 min,and the pseudo first-order kinetic constant was 4.02 h^-1,which was 5 times that of bulk g-C₃N₄.And the reaction constant per unit specific surface area was increased to 1.8 times that of monomeric g-C₃N₄.The PL test showed that the photogenerated electron-hole recombination rate of the homojunction prepared by the appropriate ratio of MCA was lower than that of the monomer g-C₃N₄. Free radical capture experiments showed that photo-generated holes were the main active species in the photocatalytic degradation process.Combined with XPS valence band spectroscopy tests,it was proposed that the homojunction photocatalysts had a Z-scheme electron transport mechanism.