A series of efficient and stable Z-scheme LaCoO3/g-C3N4 heterojunction photocatalysts with different weight contents of g-C3N4 had been first successfully fabricated by a facile one-step impregnation method. The crystal structure, surface state, element distribution and photoelectronic properties of the as-prepared samples were characterized by XRD, FT-IR, XPS, SEM, TEM, UV-Vis DRS, PL, photocurrent testing and EPR technique. The results show that Z-scheme heterostructures have formed on the interfaces between the perovskite-type oxides LaCoO3 and the flake-like g-C3N4, which enhance the visible-light absorption, separation of the photogenerated electron-hole pairs and transformation of the photogenerated electrons. Moreover, the LaCoO3/g-C3N4-60 wt% composite photocatalyst presented the highest photocatalytic activity for the degradation of phenol under visible light, whose phenol degradation rate is 85% after 5 h under visible light irradiation, which is about 5.2 and 7.5 times higher than that of bare LaCoO3 and g-C3N4, respectively. What's more, the LaCoO3/g-C3N4-60 wt% composite also shows an excellent stability. The highest photocatalytic activity can mainly attribute to high charge carrier separation efficiency as well as the improved dispersity via the Z-scheme LaCoO3/g-C3N4 heterostructure and a possible mechanism for photodegradation process over the Z-scheme LaCoO3/g-C3N4 heterojunction photocatalysts has been proposed.