Abstract: Flexible low-frequency transmission has broad application prospects in offshore wind power transmission. However, the characteristics of reactive power and control strategy should be studied further. In this paper, a mathematical model for reactive power/voltage of offshore wind power low-frequency transmission system is first established. Secondly, the objective function to reduce the maximum current and power loss of submarine cable is established, and the reactive power-voltage coordinated control strategy is proposed. Finally, a simulation model of the flexible low-frequency transmission system with offshore wind farm integration is built in PSCAD/EMTDC. The simulation results indicate that the proposed reactive power optimization control strategy has the advantages of fast and flexible response, and does not require the installation of additional reactive power compensation devices. The research results demonstrate the effectiveness of the proposed optimization control strategy.