The invention provides a deep eutectic solvent for a flow battery, an electrolyte and the flow battery, and the deep eutectic solvent is prepared by the following steps: uniformly mixing a hydrogen bond receptor and a hydrogen bond donor at a molar ratio of 1: 2, and adding one or more of the following additives after a heating reaction: the mixed solution of EC and DMC, non-noble metal ions withcatalytic action and polar gas. The diffusion coefficient of ions in the electrolyte of the flow battery can be improved, the internal resistance of the battery is reduced, and the charge-discharge performance of the battery is improved.