A dual phase-coincidence-detection time difference (DPTD) system for frequency standard comparison is proposed in this paper. Based on the concept of the greatest common factor frequency and a high-stability common frequency source, a high-resolution phase comparison between frequency standards can be implemented by utilizing the phase coincidence detection approach. The resolution of this simple instrument is better than 10 ps and the resolution of theoretical analysis is much higher than 10 ps. Compared with dualmixer time difference systems, a comparison system based on this method is simple in structure and low in cost.