The theoretical design, fabrication and characterisation of integrated optical phase-modulated Mach-Zehnder Interferometer(MZI) chemical sensing platform are presented. The sensor system, based on silica waveguide materials, is fabricated with ‘silicon microelectronics technology’. The optical waveguides are designed to mono-mode behaviour and high surface sensitivity. These sensor show a effective refractive index detection limit of 10-7. When the sensing waveguide is chemically modified, the sensing platform will show high sensitivity to opto-chemical reaction.. Finally, the refractive index resolution and sensing properties are simulated and analyzed, also, the coming key problems are discussed.