Effect of limited velocity on traffic flow is studied with cellular automaton.The simulation indicates that a saturated traffic flow determined by limited speed exists.The limited velocity results in various phase separations.In a fixed model,as the car density is low,two free-flow phases occur.As the density is high,a separation of maximum traffic flow phase from a free flow phase is observed.In an random model,as the density is high,a maximum flow-jamming-free flow appears.The traffic flow and critical density are given.