At present, microwave two-way time comparison technology is widely used in the field of inter-station time synchronization in the line-of-sight area, which can reach the nanosecond level. The application scenarios with higher time synchronization indicators need to be further improved. In this article, based on wideband signal modulation and demodulation technology, a microwave two-way carrier phase time comparison system is designed by taking advantage of the bandwidth spread spectrum signal and carrier phase measurement. The measurement uncertainty of the system is 0. 27 ps and the resolution of 4 ps is verified by using a hydrogen atomic clock and phase offset generator under laboratory conditions, which achieves the expected effectiveness. It provides a solid technical and experimental foundation for subsequent long-distance experiments and application promotion.