A high proportion of wind power generation is integrated into the grid through power electronic devices，which lack the inertial response of traditional synchronous generators. This limitation makes it challenging to maintain system frequency stability under external disturbances. Grid-forming direct-drive wind turbines operate with virtual synchronous control，enabling frequency support without interference from the phase-locked loop. To mitigate significant frequency and power fluctuations in grid-forming direct-drive wind turbines under virtual synchronous control，an active frequency support control strategy with adaptive inertia and damping is proposed. Firstly，mathematical model and small-signal model of the wind turbine system are established. Key parameters in the grid-side control loop are analyzed using characteristic root locus analysis to evaluate the impact on system frequency response. Based on this analysis，a parameter-adaptive frequency support control strategy is formulated. The validity of the small-signal model and the effectiveness of the proposed control strategy are verified through simulations on the MATLAB/Simulink platform. The results indicate that the proposed strategy effectively mitigates the frequency and power fluctuations induced by disturbances in the system.