Abstract: Very Long Baseline Interferometry （VLBI） technology requires a stable frequency datum for high-precision angular measurement in lunar and planetary explorations. A multi-user frequency transfer system for VLBI stations using only single optical fiber is designed. It realizes full-automatic fast round-trip correction phase loop without PLLs, using mixer and circulator to deliver stable standard frequency signal to antennas. The system has both real-time compensation mode and post compensation mode, and supports multiple receivers to meet the needs of VLBI stations with multiple radio telescopes. The practical results show that the frequency stability reach 10⁻¹⁷/day level within the ability to the 10⁻¹⁹ in real-time compensation mode and 10⁻¹⁸/day in post compensation mode. VLBI observation for radio source and HX-1 shows that the clock rate difference is reduced to 10⁻¹⁴ level, which can effectively reduce errors. The requirements that multiple antennas share the same oscillator has been fulfilled. At present, the system has been applied in VLBI deep space TT&C and EOP observation, maintaining high reliability.