Herein, MIL-88A/g-C3N4 (M88/g-C3N4) metal-organic framework heterojunction photocatalysts were synthesized by a facile hydrothermal method. The as-prepared samples were characterized by XRD, SEM, TEM, XPS, and DRS, and related characterization proved the intimate contact between g-C3N4 and M88. The M88/g-C3N4 photocatalyst displays excellent photoactivity for Rhodamine B (RhB), tetracycline and phenol under visible light irradiation. The M88/g-C3N4-10 exhibits the best photoactivity, and the degradation rate constant for RhB is 0.15985 min(-1), which is about 4.7 and 253 times higher than pristine g-C3N4 and M88, respectively. The enhanced photoactivity can be attributed to the formation of direct Z-scheme heterojunction between g-C3N4 and M88, which facilitates the separation of photoinduced charge. And the dominant active species and possible photocatalytic mechanism were also discussed.