The invention discloses a method for synthesizing high-purity 1,4-butane sultone. The steps are as follows: 1. Add 4-chlorobutanol and sodium sulfite solution into an alcohol solvent, heat up to reflux for 6 hours, After the reflux is completed, the mixed solution A is obtained. Concentrate the mixed solution A to recover the alcohol solvent, then add hydrochloric acid to acidify, concentrate until the material becomes viscous, then add the alcohol solvent, precipitate sodium chloride crystals, filter, and concentrate the filtrate to recover the alcohol Solvent to obtain 4-hydroxybutanesulfonic acid; 2. Continuous flash dehydration of 4-hydroxybutanesulfonic acid at a vacuum degree of 1-8mmHg and a temperature of 130-165°C to obtain industrial grade 1,4-butane 3. Add azeotrope to industrial grade 1,4-butane sultone, and recover the azeotrope by fractional distillation at normal pressure, then carry out fractional distillation under reduced pressure at a vacuum of 2-4mmHg, and collect 120 ‑121 °C fraction to obtain high-purity 1,4‑butane sultone. The method is simple and environment-friendly, greatly improves the sulfonation yield, and greatly improves the purity and yield of 1,4-butane sultone.