Abstract: When employed in operating scenarios where the weak grid is susceptible to significant power angle swings and the transmission lines exhibit a high impedance ratio, the virtual synchronous generator (VSG) encounters severe coupling between active and reactive power. This coupling can potentially lead to power steady-state errors, dynamic oscillations in the VSG, and in severe cases, even system instability. By establishing a wide frequency domain dynamic power coupling model of the virtual synchronous generator, the dynamic relative gain array is used to analyze the VSG power coupling mechanism. On this basis, a virtual synchronous generator power decoupling strategy based on adaptive dynamic virtual synchronous impedance is proposed, which can dynamically eliminate the coupling effect between VSG power loops. Through the comparative analysis of the small signal model, it is proved that the decoupling strategy can effectively improve the stability of the VSG system. Finally, the PSCAD/EMTDC simulation verifies that the proposed method can not only effectively eliminate the power coupling, but also further improve the VSG power dynamic response performance.