The invention relates to a preparation and purification method of ion-pair chromatographic reagent sodium pentanesulfonate. The specific steps of the preparation and purification method are: into a reaction vessel, the molar ratio is 1:25:0.65:(0.004~0.006) Add anhydrous sodium sulfite, water, pentane bromide, and tetrapropylammonium bromide in sequence, heat and reflux until the reaction liquid is clear and not stratified; evaporate the water in the reaction liquid under reduced pressure, dry the remaining solid, crush it, and put it into Extract in a Soxhlet extractor, then recrystallize the crude sodium pentanesulfonate obtained from the extraction, filter to obtain the pure product, and then dry it in vacuum to obtain the finished product. In the invention, anhydrous sodium sulfite and bromopentane are subjected to sulfonation reaction under the action of catalyst tetrapropylammonium bromide, and then purified and dried to generate high-quality sodium pentanesulfonate. The method is simple and easy to implement, low in cost and short in reaction time, and the generated sodium pentanesulfonate has good solubility, high purity, product content ≥ 99.6%, stable and reliable quality, and can fully meet the special requirements of high-performance liquid chromatography.