Base on the case study of three coastal beaches in south China, the sensitivity of multi-channel rip currents to the bathymetry and the wave conditions was checked by groups of numerical simulations using the Boussinesq phase-resolving model. The time-averaged velocity, vorticity, and surface elevation were computed and analyzed. Results indicate that the rip strength was in direct proportion to the incident wave height and the channel width. The rip current might be totally absent in small channels when the majority of water flows out through neighboring broader pathways. Alongshore currents prevailed over the rip current when the incident wave angle reached 11 degrees, which was not favorable to the existence of channeled sandbars. Vortices appeared around the edge of the bar crest due to nonuniform wave breaking over the rapid-varying bathymetry. The strong spin of the flow was significantly intensified and stretched along the sandbar array as the wave direction deflected. The setup water was held landward largely by the sandbar and substantially increased with the wave angle. There was no water surface depression in the rip channel as the angle increased, which fundamentally explained why the rip current could not persist when the incident wave became slightly oblique.