With the development of high precision optical clock and its various applications, higher and higher precision is needed for time-frequency transmission technology. Time-frequency transmission technology based on optical fiber has been relatively mature, while the time-frequency transmission technology based on free-space laser can be applied to the fields of inconvenient laying of optical fiber, fast maneuvering, and time-frequency transmission between the satellite and the Earth and between satellites. This paper introduces the research status of near-earth space and time-frequency transmission between the satellite and the Earth, and the development trend is also prospected. In the future, free-space laser time-frequency transmission will develop towards higher transmission accuracy, time-frequency transmission, ranging, communication integration, and time-frequency space networking.