The diode rectifier unit-based high voltage direct current (DRU-HVDC) integration scheme has gradually become popular for large-scale offshore wind farms (OWFs) due to its advantages in terms of low cost and lightweight. However, the traditional grid-following (GFL) control strategies of wind turbines (WTs) cannot be used since DRU lacks the grid-forming ability. Therefore, the current research mainly focuses on the grid-forming (GFM) control strategies for WTs to establish the offshore grid. However, the harmonic and resonance characteristics of the offshore grid receive relatively less attention. Accordingly, this paper proposes a parameter design method for the circuit and WTs’ control parameters by considering system harmonic and resonance characteristics. Furthermore, simulation results based on PSCAD/EMTDC have been provided to verify the effectiveness of the proposed design method.