Fabrication method of large core polymeric optical waveguides by three-time replication of anisotropically etched (110) single-crystal silicon original molds is proposed. Those replication processes consist of soft lithography, UV embossing and hot embossing. Original masters for this replication process were fabricated by anisotropic etching of (110) single-crystal silicon wafers by a strong alkali solution. The optimum conditions of anisotrophic etching are etching temperature of 60° C and the alkali solution concentration of less than 30wt%. Original masters replicated to silicone rubber molds by soft lithography. Then, using UV embossing, the silicone rubber molds replicated to an UV-curable resin for hot embossing stampers. The stampers by hot embossing replicated to rectangular groove PMMA replicas that act as undercladdings for optical waveguides. The optimum conditions of hot embossing are the heated temperature of over 130° C, the pressure of more than 50kgf and the removal temperature of less than 110° C. In this work, channel optical waveguides with 100, 300, 500 μm core size were fabricated by controlling the pattern width of silicon and etching time of silicon. Low Propagation losses of 0.30, 0.22 and 0.19dB/cm at 650nm were realized for 100, 300, and 500 μm core waveguides, respectively.