The low-frequency alternating current transm ission system for offshore wind power based on a diode rectifier unit （DRU） is a novel technical scheme with application prospects for the grid connection of deep-sea offshore wind power.Due to the uncontrollability of DRU，the operation state of the low-frequency alternating current system is controlled by wind turbines using grid-forming amplitude-phase control mode.To analyze the relationship between system operation state and wind power control characteristics，a power flow calculation model of the DRU-based low-frequency alternating current transmission system for offshore wind power was established.Definite conditions and equations to be solved were determined according to the system operation control mode，which accurately reflects the steady-state operation condition of the system under given wind power control.Based on the established power flow calculation model，the sensitivity of amplitude-phase control mode and the system operation state under different output levels were analyzed，and the system power flow under different reactive power control strategies was compared.The analysis results provide a good reference for engineering planning and system control design.