The flame-retardant gel polymer electrolytes present great potential for application in alkali metal batteries due to their high safety characteristics, such as good ability of dendrite inhibition, non-leakage, and non-flammability. This paper reviews the advances of flame-retardant gel polymer electrolytes in various alkali metal batteries, including lithium, sodium, aluminum, zinc, etc. The paper first discusses the flame-retardant mechanism of gel polymer electrolytes. Subsequently, the common preparation methods of flame-retardant gel polymer electrolytes are highlighted. Furthermore, the advancements of different-type flame-retardant gel polymer electrolytes in different alkali metal battery systems are symmetrically discussed. Finally, their current challenges and potential development directions are significantly proposed.