The offshore wind power is becoming an important development direction in the field of wind generation. In offshore wind farm, submarine cables are widely used to transmit power, which makes the resonance problem more serious due to the cables’ high grounding capacitor. The power collecting system determines the cables’ length, electric parameter and connection type, which directly affects the resonance frequency and impedance. This paper builds the resonance model of offshore wind farm transmission system, including wind generators, cables and transformers. Using modal analysis method, the resonance situations under different power collecting systems are simulated and calculated. The key nodes causing resonance are located by the participation factor. The main parameters’ influence on resonance is evaluated with parameter sensitivity analysis. Finally, the filtering solution is proposed for different resonance frequency, which is proved to be effective by simulation results. This work is supported by National Natural Science Foundation of China (No. 51477098 and No. 51307106).