The time synchronization accuracy depends on the accuracy of the transmission delay measurement of the time signal in the time transfer system. The transmission delay is always achieved by measuring the round-trip path delay using the outgoing and incoming path. But it incurs error due to the chromatic dispersion of the fiber in the time transfer system based on optical cable. A method to count the difference in transmission delay between the outgoing and incoming path is proposed based on the dispersion of the G.652 fiber. The error caused by fiber dispersion can be eliminated when the wavelength of optical signal in the round-trip is around 1.55-μm by using this method, which can achieve the accurate transmission delay of the signal.