Quasi-velocity-matching can be used to realize electron-optics phase modulator with high modulation index, which has essential applications in spectroscopy, laser frequency conversion and improving laser beam uniformity. When laser beam with high power propagates through the modulator, the larger aperture of the device is necessary, so the poling technology on ferroelectric crystal with large-area and high-thickness is essential for high power quasi-velocity-matching. In this paper, the electrical-poling process in room temperature on LiTaO3 crystal with the thickness of 1mm is studied in detail. In order to restrain back current during poling process, control of electrical poling time is adopted in the experiments. large-area domain inversion of LiTaO3 is successfully realized proved by thermoelectric effect and chemistry etching method. The proposed technology can be also employed in other ferroelectric crystal poling.