Mountain wind farms are limited to topography, wind energy distribution and other factors. They usually have a complex collector structure and diversified electrical connections, which leads to cumbersome harmonic modeling of wind farms and difficult harmonic resonance analysis. Therefore, based on the actual mountain wind farm topology, the current collection structure is divided into three types, and the transfer function model is established to systematically study the coupling resonance phenomenon and the mechanism of mountain wind farms. Firstly, it reveals that internal resonance, inner resonance, external resonance and cross-regional resonance widely exist in mountain wind farms. For the three collector structures, the control resonance band, the filter resonance band and the superimposed resonance band are distinguished in a wide frequency domain. Then, the harmonic amplification caused by each resonance band in the above four resonances is analyzed, and it is found that in the cross-regional resonance, the resonance frequency band is broadened and tends to high frequency. Further considering the change of the harmonic propagation path, the harmonic conduction coefficient is defined to describe the amplification mechanism of the coupled harmonics propagating through different paths. Finally, simulations verify the correctness of the theoretical analysis and modeling.