Lithium-sulfur (Li-S) batteries have become one of the most promising next-generation battery systems due to their high energy density and low cost. However, the application of Li-S batteries still faces critical challenges, such as the low conductivities of S and Li₂S, shuttle effect of polysulfides and dendrite growth of Li, etc. The optimization of the electrolyte can ameliorate the electrolyte|electrode interphase, conveniently regulating the parasitic reaction and improving the performance of the resultant batteries. The functional additives in electrolytes provide chances to tune the interphase and even the redox mechanism to improve the performance of the batteries. In this review, we systematically summarize the latest progresses of additives for Li-S batteries. The additives are classified according to the category that lies on the protection of Li metal anode or the stabilization of S cathode. The functions of additives on the S cathode such as the inhibitions of dissolution and shuttle of the polysulfides, the redox mediators, and the activation of Lii₂S deposits are discussed in detail. Finally, the prospects of additives for Li-S batteries are supplied in brief. We hope that the review can provide a guidance in the design of electrolyte for high-performance Li-S batteries.