A method for measuring distance involves calculating a distance based on light speed and a time taken by an optical signal to travel to an object and return therefrom. The method includes calculating a time based on a cycle number of a reference signal under a clock mask synchronized with emission and reception of the optical signal; correcting the time according to a plurality of phase shift signals generated based on the reference signal; and minimizing an error of the time by increasing the quantity of the phase shift signals. The method enhances the accuracy of the measured time taken by an optical signal to travel to an object and return therefrom, speeds up measurement, and reduces the required circuit areas. A system for measuring distance is further introduced for use with the method.