Ultrathin graphitic phase carbon nitride (g-C3N4) was prepared by a simple thermal polymerization method using melamine as the precursor. The two-dimensional bismuth iodide/graphite phase carbon nitride (2D/BiOI/g-C3N4, BICN-x) Z-type heterojunction with different BiOI mass ratios were compounded and constructed by in situ deposition-precipitation method to generate bismuth iodide (BiOI) on the surface of g-C3N4 for synergistic persulfacte (PS). The structure, surface functional groups, morphological characteristics, specific surface area and optical properties of the photocatalysts were characterized by XRD, FTIR, SEM, HRTEM, BET and UV-vis DRS. The results showed that the photogenerated electron-hole pair separation efficiency was higher when the mass ratio of BiOI to g-C3N4 was 2:1 (BICN-3) through close interfacial coupling, the photogenerated e- reached the surface of the structure with a faster migration rate, and the catalytic system formed by BICN-3 and PS (BICN-3/PS) removed 88.2% of tetracycline (TC, 10 mg/L), with a degradation rate 3.82 times higher than that of BICN-3 alone.