The work aims to study effects of temperature on grinding and thinning process of LiNbO3 crystal plate. Horizontal grinder was used to reduce the thickness of LiNbO3 crystal plate to 80 μm. The speed of cup wheel was 200 r/min and feed rate of workpiece was 0.002 mm/min. A homoeothermic water-bath device was used to ensure that machining temperature was constant. The LiNbO3 crystal plates are grinded at different ambient temperature: 25, 45, 60, 75 ℃. The grinding affected its deformation and rupture. The LiNbO3 crystal was single-crystal at 25 ℃ and both single- and multi-crystal at 45 ℃. The proportion of multi-crystal structure increased while single-crystal structure decreased as temperature rose. Therefore, temperature had a significant effect on changing microstructure of LiNbO3 crystals. The study object was simulated based upon piezoelectric module and multi-field coupling function of COMSOL Multiphysics simulation software. The simulation indicated that, as temperature rose, both deformation displacement of LiNbO3 crystal chips and stress carried by the chips increased gradually, stress along the edges was the maximum. Temperature can directly affect internal structure of LiNbO3 crystal chips and even result in the increase of deformation displacement, so temperature should be controlled to avoid its negative effects.