To provide a novel stabilization method for suppressing over-time denaturation of a high-purity ethylene carbonate-containing composition, a stabilized high-purity ethylene carbonate-containing composition, and the like. A method for stabilizing a high-purity ethylene carbonate-containing composition includes adjustment of content of the total of formic acid and a formic acid salt, or 2-chloroethanol to 500 ppm by mass or less in the high-purity ethylene carbonate-containing composition including 90% by mass or more ethylene carbonate.