A system for optimum phase searching in an Ethernet physical layer includes a time recovering circuit and an equalizer. The time recovering circuit includes a loop filter and a time error detector, and the equalizer includes a feed forward equalizer, a slicer and a feed backward equalizer. An optimum phase searching method includes obtaining optimum phases when mean squared errors calculated by the slicer are less than a first threshold, absolute values of mean values of outputs calculated by a time error detector are less than a second threshold, and the outputs are monotonic.