The ion conducting pore of potassium channels can open and close to regulate the ion passage, was Iongly thought to be a one-dimensional pore structure with a water-filled central cavity.Here we find four orifices in the KcsA potassium channel, perpendicular to the pore, outstretched from the cavity.Equilibrium molecular dynamics simulations show that water molecules can flow between the cavity and orifices.Targeted molecular dynamics simulations up to 60 ns show that during opening process, water molecules can move into the cavity through the orifices to facilitate channel gating, while blocking the aqueduct orifices makes the channel difficult to open.