Two different configurations, reflection and transmission, of Mach-Zehnder interferometer(MZI) are introduced for the measurement of the electro-optic coefficients in a poled polymer thin film. The MZI measurement of the electro-optic coefficients has an advantage of permitting the determination of the electro-optic tensor coefficients, r13and r33, independently, when compared with the single-beam polarization interferometer. In the reflection configuration of two beam interferometric measurement, a proper consideration of the optical path change, due to the reflection angle change, is found to be critical in determining the absolute value of the electro-optic coefficients, while the transmission configuration allows the independent determination of the electro-optic coefficients in the direction of the ordinary and the extraordinary optic axes.