In this study, g-C3N4/Ag/Ag3PO4 composites were constructed by a simple in situ deposition method at room temperature, in which Ag3PO4 particles with regular rhombic dodecahedrons morphology were finely coated on the surface of the g-C3N4 sheet. The g-C3N4/Ag/Ag3PO4 exhibited much improved activity comparing with other classic catalysts such as g-C3N4/ and Ag3PO4. The optimal photocatalyst (AC(1.0)) with Ag3PO4/g-C3N4 ratio of 1 could dramatically decompose phenol under visible-light irradiation, which showed a degradation rate of 1.13 min(-1) and almost 60 and 2.5 times higher than that of pure g-C3N4 and Ag/Ag3PO4, respectively. After 3 cycling run tests, the AC(1.0) photocatalyst still maintained high photocatalytic activity. Electron paramagnetic resonance spectroscopy and radical quenching tests were employed to investigate hydroxyl and superoxide radicals for organic degradation processes. Furthermore, the photocatalytic activity of AC(1.0) was also tested for gaseous isopropanol (IPA). After 4 h irradiation, 63% of IPA was oxidized with acetone as main outcome product. The highly efficient separation of photogenerated electron-hole pairs was attributed to the construction of Z-scheme mechanism.