To investigate the influence of temperature field of friction stir welding (FSW) 2219 aluminum alloy thick plate, and to achieve effective prediction of temperature field, the authors establish a three-dimensional numerical simulation model of FSW 18 mm thick 2219 aluminum alloy based on ABAQUS/CEL, considering the morphological characteristics of the tool pin. The simulations of plunging, dwell-ing, and welding stages are achieved. The distribution of temperature and temperature cycle curve of characteristic points in welding process are obtained. The validity of the simulation results is verified by experiments. The influence of the tool-rotational speed and welding speed on temperature field is explored. The work lays a foundation for the prediction and control of temperature field in FSW medium thickness 2219 aluminum alloy, and provides reference for selection of welding parameters to ensure high quality welding of fuel tank of heavy-lift rocket.