The invention discloses a shielded twisted pair cable structure and a preparation method thereof, include a first lead, second conductor, A first dielectric insulator, A second dielectric insulator, Athird dielectric insulator, A shield layer and a fourth dielectric insulator, the invention adopts silver ammonia method, growing a conductive silver layer on the surface of the third dielectric insulator, A photolithographic mask method is adopted to pattern the silver layer of the third dielectric insulator with conductive silver layer, thereby forming a shielding layer and realizing the in-situ growth of the shielding layer on the interposition insulating layer. The shielded twisted pair cable structure preparation method is more convenient, and has the advantages of simple structure, firmadhesion of the electromagnetic shielding layer and the conductive insulating layer, and high shielding efficiency.