Optical second harmonic generation in the form of Cerenkov radiation is investigated using KH2PO4 (KDP) substrate and poled polymer thin film waveguide. The copolymer of MMA and DR1-substituted methacrylate molecules were oriented by corona poling precess after spin coating on the KDP substrate. The conversion efficiency strongly depends on the waveguide geometry. The high conversion effficency is obtained by theoritical analysis when the nonlinear optical coefficient direction of a substrate is opposite to that of a waveguiding layer. In experiment, we haveconfirmed that the SH power by Cerenkov type phase matching using KDP crystal as a substrate is larger than that of using pyrex as a substrate.