Provided are a preparation method for insoluble sulfur and an anti-reversion stabilizer used thereby. Methane is used as the anti-reversion stabilizer. The methane is added to liquid sulfur at sulfur gasification stage, and is cracked into active free radicals under the action of sulfur vapor active free radicals; in the quenching process of sulfur vapor mixed with methane, the active free radicals generated by methane cracking carry out end capping on insoluble sulfur end groups generated by sulfur vapor polymerization, thus completing insoluble sulfur stabilization. The methane is added at liquid sulfur gasification stage, and after sulfur gasification, the methane is mixed with sulfur vapor in a gaseous form, rather than being added to the product in a solid or liquid manner at a later stage, so that the insoluble sulfur and the stabilizer can be uniformly contacted and mixed to the greatest extent.