The cycle life of aqueous Zn-metal batteries is greatly challenged due to the formation of Zn dendrites on the electrode surface and side reactions. Herein, an effective tactic against the above problems was proposed by adding 1,3-dimethyl-2-imidazolidinone (DMI) to the ZnSO₄ electrolyte to form an inert organic layer on the surface of the zinc foil, and the protective mechanism of DMI molecules on the surface of zinc poles was discussed by density functional theory. The formation of this inert layer can protect the zinc foil from being eroded by H₂O, homogenize the electric field on the electrode surface and inhibit the formation of dendrites. The addition of DMI also destroys the original hydrogen bond network in the system and suppresses the side reaction problem caused by the Grotthuss mechanism. This new electrolyte can effectively improve the cycle performance of different half-batteries. In ZnSO₄-DMI-05 electrolyte, the Zn||Zn cell achieved stable cycling for 2400 h at a current density of 1.0 mA cm⁻² (1.0 mAh cm⁻²). Furthermore, it was applied to a Zn||VS₂ full cell and cycled for 600 cycles at a current density of 1 A/g, achieving a coulombic efficiency (CE) of 99.97 % and a capacity retention rate of 95.33 %. This organic additive enables ultrastable and reversible deposition of zinc ions on different types of substrates in an aqueous environment, providing a promising approach for the development of aqueous zinc-metal batteries.