A multiple transmission channels, heterojunction and 3D PCN/AgBr/rGO photocatalyst was successfully synthetized by introducing the reduced graphene oxide (rGO) covering AgBr onto the surface of 3D porous g-C3N4 (PCN). In PCN/AgBr/rGO, PCN as a semiconductor photocatalyst provides the 3D framework, the heterojunction was formed with AgBr particles and PCN, rGO promotes the electron transfer simultaneously and introduces a multiple transmission channels system to increase the active species. Thanks to the heterojunction formed between PCN and AgBr, resulting rapid separation of photo-generated e(-)/h(+) at interface. The 3D PCN/AgBr/rGO nanocomposite exhibits excellent photocatalytic efficiencies for tetracycline (TC) up to 78.4% within 90 min and 2,4-dichlorophenol (2,4-DCP) up to 68.2% within 6h. The photocatalytic rate of PCN/AgBr/rGO was much higher than 3D PCN (21%), AgBr particles (31%) and most of g-C3N4-based photocatalysts in TC degradation. Moreover, the PCN/AgBr/rGO shows high photocatalytic stability due to the significantly photocatalytic stability after four photo-degradation cycles. This study highlights the potential application of PCN/AgBr/rGO highly efficient waste water purification.