Abstract: Large-scale offshore wind farms have become the development trend of wind power generation. Submarine cables, of which the distributed capacitance cannot be ignored, are used to collect electrical energy in collector network of offshore wind farms. The impedance of collector network is complex and changeable, which will lead to a risk of high frequency harmonic resonance (HFHR) when interacting with the impedance of the wind turbine generators (WTGs). In turn, the HFHR may threaten the safe and stable operation of wind farms. To address this problem, firstly the impedance of the collector network was constructed. Furthermore, the collector network of a wind farm was divided into the equivalent wind turbine subsystem (EWTS) and the remaining equivalent wind farm subsystem (REWFS). Then, the mechanism of HFHR was revealed. The effects of cable parameters, the number of chain circuits, the number of connected WTGs, and the grid impedance on the HFHR of the interconnected system were analyzed. Taking an offshore wind farm as the research object, the MATLAB software and RT-LAB-based hardware-in-loop experiments were used to analyze the wind farm, and the results can verify the correctness of the theoretical analysis.