An integrated optic Mach-Zehnder interferometer (MZI) sensor which uses the ZPU44and ZPU46polymers as the core and upper cladding materials is designed and fabricat ed.The structure parameters,including as the waveguide cross section shape,bending radius and the length of the sensing window,are designed and optimized.Also the refractive index sens ing properties are analyzed and then the designed polymer Mach-Zehnder interferometer sensor i s fabricated using the traditional mirco-fabrication technology,namely,the contact p hotolithography and reactive ion etching (RIE).The measuring results show the polymer Mach-Zehnder interferometer sensor has a linear response to the refractive index changing from 1.33to 1.44, and the sensitivity of the sensor can reach the value of 88dBm/RIU,which matche s the theoretical results well.The length of the sensing area is very small and th is polymer sensor can be integrated easily and has wide prospects for applications in the chemical and biological sensor fields.