In order to solve the problem of low accuracy of long-distance transmission in fiber optic time transfer system, the basic principles and technical characteristics of four mainstream high-precision fiber optic time transfer methods, namely round-trip, dual-fiber bidirectional time synchronization, bidirectional wavelength division multiplexing and bidirectional time division multiplexing, were analyzed. Based on this, a single-channel time-frequency transmission device was developed. The device adopts the electrical phase compensation method to realize frequency transfer synchronization, and uses the round-trip method combined with bidirectional time division multiplexing to achieve time transfer synchronization. It uses 1 PPS and 100 MHz to jointly mark the time signal, with 1 PPS as the coarse time marker and 100 MHz as the fine time marker, to achieve high precision time synchronization. Experiments show that the uncertainty of the single-channel time-frequency transmission device is about 13 ps, which can meet the requirements of the existing fiber optic time-frequency synchronization network metrology calibration. The device has broad application prospects in the fields such as cascaded time transfer synchronization and fiber optic time-frequency synchronization network metrology calibration. It provides an important technical support for the construction of high stability, high reliability and high precision time service system.