The invention relates to a technological method for manufacturing a polymerization inhibitor in polymeric additives, and aims to provide a process for manufacturing a polymerization inhibitor 708 with a one-pot method so as to fill up a gap in the industry. According to the process for manufacturing the polymerization inhibitor 708, the one-pot method is used; and by the aid of the solid catalyst one-pot method, the reaction efficiency can be effectively improved. The process is combined with actual production, so that the previous multi-step reaction is replaced; and moreover, a liquid catalyst is replaced with solid base. The process is mainly applied to clean production, the quality is improved, and the effects are increased.