Considering the high cost of the production of semaglutide, which is currently the most promising antidiabetic drug especially for the treatment of type 2 diabetes mellitus, a new synthetic route of semaglutide production that possesses excellent yield and high purity is of vital importance. Herein, we reported a newly developed synthetic route of semaglutide that is simple and efficient, based on a soluble hydrophobic-support-assisted liquid-phase synthetic method by applying Alloc-chemistry to the synthesis of the main chain peptide and side chain peptide of semaglutide. With careful optimization of the reaction conditions and innovative strategy of post-synthetic treatments, the total yield and purity of the crude semaglutide was improved satisfactorily.