A duty cycle correction method includes detecting independently a relative delay time of two input differential signals; equating the sum of two relative delay time with the cycle of the input differential signals; and adjusting the two delay time to the same value. A corresponding implementation circuit includes two time delay units; two relative phase detectors connecting simultaneously with each of the two time delay units; a charge pump connecting with the output of each of the two relative phase detectors, with its output connecting to the two time delay units in order to form a loop; and a synthesis output unit connecting with both the time delay units, thereby generating output signals. The adjusting range of duty cycle becomes much wider. The implementation circuit is absolutely symmetrical, so a duty cycle with high accuracy can be obtain.