On the platform of large gantry machine tool, temperature and thermal error measuring system was developed with the aim to compensate thermal error of large machine tool. Then thermal error and temperature field were measured and temperature variables for modeling were selected based on the analysis of correlation between thermal errors and temperatures. Finally, thermal error model of Z direction was set up with multi-variable regression and the subsequent thermal error variation was predicted with the model. The results show that the model can effectively reduce thermal error from 60 μ m to 18 μ m. Thus the feasibility of the model is verified.