Abstract: To make the wind power have the function of inertia support and primary frequency regulation as the conventional power source, for the direct-driven wind turbine with energy storage in parallel on the DC side, this paper proposes a grid-forming control structure. Then, according to the frequency modal analysis method, the small-signal stability margin quantitative method is presented considering the dynamic interaction between the machine-side, grid-side, and energy storage converter. On this basis, the interaction mechanism is revealed adopting the complex power coefficient method. The impacts of two inertia support methods, namely based on the wind turbine kinetic energy and battery energy storage respectively, on the stability of the wind turbine are compared. The research results indicate that the droop control of energy storage converter can not only achieve primary frequency regulation, but also introduce positive damping to enhance the small-signal stability of wind turbines. Using the kinetic energy of the wind turbine to provide inertia support will introduce negative damping, while relying on energy storage to achieve inertia support can introduce positive damping. Finally, to further enhance the stability of the grid-forming wind turbine with energy storage, an active damping control strategy is proposed. The simulation model based on PSCAD/EMTDC is built to validate the feasibility of the proposed control method and the correctness of theoretical analysis.