The invention provides a method for synthesizing 5-bromine-3-sec-butyl-6-methylluracil, which belongs to the technical field of chemistry. The method screens a phase transfer catalyst through studying the effect of the phase transfer catalyst on reaction, so that the reactive mode in synthetic route is changed into homogeneous reaction from the prior heterogeneous reaction through phase transfer.The method compounds environment-friendly absolute ethyl alcohol and tetrabromocyclo- hexadienone as complexometric reagent based on the structure of a product, and uses paratoluenesulfonic acid as acatalyst in reaction, so that yield and reaction condition of the product have obvious improvement, and the optimal reaction condition can be obtained through optimizing technology.