Very long baseline interferometry (VLBI) is an astronomical interferometry method used in radio astronomy. It allows multiple astronomical telescopes to observe a celestial body at the same time, simulating the observation effect of a giant telescope with the size equivalent to the maximum distance between telescopes. The basis of very long baseline interferometry is time synchronization and phase synchronization. Time synchronization means that the two observation antennas have the same time, while phase synchronization means that the received frequency signals have the same phase, which is actually time synchronization. The principle of very long baseline interferometry is to record the mixed signals of two stations on the magnetic tape of each station (instead of a common clock, each station has its own clock, and the time scale signal is also recorded on the magnetic tape). After the observation, the tapes of the two stations will be sent to the processing system for data playback and related processing. In this way, as long as the source can be seen at the same time, the length of the baseline is almost infinite.