This paper describes a novel simple process suitable for fabrication of grating coupler on the optical waveguide using silicon mold. The mold was fabricated using electron beam lithography and fast atom beam etching. Submicron grating patterns were transferred from silicon mold to polymer waveguide layer. In the transfer, grating coupler and waveguide was fabricated simultaneously by the mold at room temperature in the air. In the proposed method, the good replication in submicron region is realized by the casting method without pressing. Maximum coupling efficiency 25% was obtained. This technique can also be used to fabricate other nanometer-scale structures. Keywords: Grating Coupler, silicon mold, waveguide.