A micro biochemical sensor based on a SOI optical waveguide sensing platform is reported in this article. The sensing platform utilizes a Mach-Zehnder Interferometer (MZI) configuration. In order to satisfy the single-mode transmission condition of the waveguide and match the coupling size of standard single-mode fiber, a ridge waveguide structure is adopted to construct the MZI configuration. The key parameters of the waveguide are optimized by FDTD method. A process composed of contact exposure photolithography and Inductively Coupled Plasma (ICP) etching technology has been worked out for the fabrication of the optical waveguide sensing platform on SOI wafer. In the process, only one photolithographic mask is used. The mask is designed to have several patterns including an array of MZI configurations for multiple species sensing, a group of ridge waveguides with different key parameters as test references, and a group of geometric compensation schemes to test the methods of modifying the deviation which may arise during the ICP etching step. Process simulations are conducted to predict the exposure and etching results, which give strong support to the fabrication process control. Lithography problems including photoresist desquamation and line narrowing are solved to achieve the special structure.