Zr-doped Zr/g-C3N4 photocatalysts were prepared by thermal polymerization using guanidine hydrochloride as the precursor and zirconium nitrate as the zirconium source. The structure, morphology and optical properties of the catalysts were characterized and analyzed by means of XRD, SEM, UV-Vis DRS, PL, XPS and BET. The results show that the Zr/g-C3N4 photocatalyst modified by Zr doping broadens the absorption of visible light, increases the specific surface area, reduces the recombination rate of photogenerated electrons and holes, and has good photocatalytic activity. Under visible light irradiation, the photocatalytic degradation rate of 5Zr/g-C3N4 had a degradation rate of 99.29% for Rhodamine B(RhB) within 60 min. The photocatalytic degradation process conformed to the first-order kinetic equation, and its rate constant k= 0.08647 min-1, which was 8.3 times that of pure g-C3N4. The trapping agent experiment found that the main active species for degrading RhB was superoxide radical, and the possible reaction mechanism was speculated.