The invention relates to a preparation method for gel for radiotherapy three-dimensional dosage verification. The preparation method comprises the following steps that oil-soluble polymeric monomer and water are mixed, and a first solution is obtained; the first solution is deoxidized and then placed into a gamma-radiation source, irradiation crosslinking is carried out, a second solution with a dissolved polymer is obtained and subjected to centrifugation and freeze drying, and polymeric microsphere solid powder is obtained; the polymeric microsphere solid powder and radioluminescent monomer are mixed in water, a third solution is obtained, water-soluble polymeric monomer is dissolved in water, and a fourth solution is obtained; the third solution and the fourth solution are mixed, subjected to deoxidization and then placed into the gamma-radiation source, irradiation crosslinking is carried out, and the gel for radiotherapy three-dimensional dosage verification is obtained. The preparation method is quick, simple, low in cost and high in yield and has no other side product, the synthetic gel has good luminous efficiency, mechanical strength and very good tissue equivalence, and dosage verification of a gel dosage meter in the clinical radiotherapy process is carried out conveniently.