The invention relates to a 1,3-propane sultone preparation method, which comprises: S1, completely mixing in a reaction container by using 3-chloropropanol and sodium sulfite as raw materials and using water as a solvent, controlling the temperature at 25-120 DEG C, carrying out a reaction for 4-48 h, carrying out pressure reducing dewatering concentration, adding concentrated hydrochloric acid tothe concentrated liquid, carrying out acidification, controlling the temperature at 0-80 DEG C, stirring for 1-24 h, filtering, and concentrating the filtrate to obtain 3-hydroxypropanesulfonic acid;S2, controlling the temperature of the concentrated liquid obtained in the step S1 at 40-110 DEG C, and carrying out pressure reducing concentrating to carry out dewatering ring closure on the 3-hydroxypropanesulfonic acid in the concentrated liquid to obtain a crude product containing 1,3-propane sultone; and S3, rectifying the crude product containing 1,3-propane sultone to obtain 1,3-propane sultone. According to the present invention, the method has characteristics of short process route, less three-waste and simple post-treatment, wherein the total yield can achieve more than 90%, and the purity of the product can achieve more than 99.9%.