The invention discloses a method for synthesis of trimethylolpropane diallyl ether. The method comprises the following steps that dioxane, trimethylolpropane and PEG-600 are added into a reactor; the mixed raw materials are heated with stirring so that the mixed raw materials are dissolved completely; solid NaOH is added into the solution; the solution is heated to a temperature of 80 DEG C; chloropropene is dropwisely added into the heated solution with stirring; the solution undergoes an etherification reaction and then is subjected to reduced pressure distillation; and dioxane and a trimethylolpropane diallyl ether product are recovered at different temperatures. Trimethylolpropane diallyl ether content of the trimethylolpropane diallyl ether product obtained by the method is more than 92%. The method provided by the invention has a high yield, high purity, a low production cost and simple processes and can satisfy industrial production demands.