A composite optical waveguide (COWG) based on polarimetric interferometer was developed. The COWG is a single-mode glass waveguide which overlaid with a tapered high-index layer such as TiO2 and Ta2O5. It can cause the spatial separation in the film-covered region of the zero-order transverse electric (TE0) and magnetic (TM0) modes that transmit along the same path in the glass waveguide, making the evanescent field with the TE0 mode much stronger than that with the TM0 mode. By using the COWG polarimetric interferometer combined with a novel prism-chamber assembly and a polarization-controllable photodetector, the model OWG-01 biochemical analyzer was developed, which is highly sensitive, reliable and convenient. Test results indicate that the response of the analyzer to refractive index of liquid reveal has a very weak thermo-optical effect on the COWG chip, and the main measurement error comes from the temperature variation of refractive index of the liquid sample.