Abstract: With the increasing proportion of doubly-fed wind turbines (DFIG) and high-voltage direct-current (HVDC) in the power system, there will be interactive stability problems when the line-commutated converter based HVDC (LCC-HVDC) is interconnected with the doubly fed wind farm and the weak grid, and the oscillation frequency will show the characteristics of frequency coupling. In order to study the frequency coupling phenomenon of LCC-HVDC rectifier station, the impedance model was established by using 3-D Fourier transform. The mechanism of frequency coupling phenomenon of LCC was analyzed, so was the sensitivity of various influencing factors to the frequency coupling degree of LCC. Finally, the influence of frequency coupling characteristics on the stability analysis of interconnected system, composed of the LCC rectifier station, doubly fed wind farm and the weak grid were studied. The conclusions were verified by time-domain simulation.