A novel fiber electro optic phase modulator has been fabricated with the thermal poling of polarization maintaining fiber. A PANDA polarization maintaining fiber polished and deposited with micro strip electrode was poled as applied DC 3000 V voltage on its both sides at temperature 280 ℃. The electro optic coefficient of the electro optic phase modulator is 0.47±0.05 pm/V. Because built from polarization maintaining fiber, the phase modulator may be used in all fiber device based on fiber interferometer with polarization stability.