A high-sensitivity y-splitter, based on thermal ion-exchange waveguide has been studied for biochemical sensing platform applications. Based on the analysis, the ion-exchange waveguide has been simulated and designed by using the finite difference time domain method (FDTD). To realize high-resolution, y-splitter read-out configuration is investigated based on the ion-exchange waveguide with a total height of 0.22 µm and width of 0.5 µm at the operating wavelength between 1500 and 1600 nm. The length of the sensitive window in the y-splitter configuration is 4 µm, where the total length of the y-splitter is 16 µm. In this context, the produced bio-sensor which can be made using the optical waveguide configurations, is providing a cost-effective method for sensing materials such as DNAs. The sensing arm which is covered by the DNA as upper cladding has 0.45 x 10−3 decreasing power in comparison to the reference arm. In this paper, the simulation of the y-splitter optical waveguide has been performed using the ion-exchange technique to detect the DNAs.