The invention provides an application of a fluorine-containing compound as a flame retardant in polylactic acid (PLLA), and a flame-retardant composition containing the fluorine-containing compound. The fluorine-containing compound, sulfonate and a DOPO flame retardant can achieve a synergistic effect to achieve flame retardance of PLLA, the flame-retardant composition comprises the fluorine-containing compound, the sulfonate and the DOPO flame retardant, the flame-retardant composition can be used as a PLLA flame retardant, and the flame-retardant PLLA has flame-retardant performance under the condition that good spinning capacity is kept.