In order to analyze the variation laws of equivalent stress, temperature and thickness of sheet metal during forming process, a thermalmechanical coupled finite element analysis model was established by hot stamping experiment of 6016 aluminum alloy Ushaped parts. The results show that the stress on the flange area outside the blank is always small. With the increase of deformation, the stress in the punch fillet region increases gradually up to maximum 54 MPa, and the maximum stress and thickness reduction are located at the punch fillet region, which is the dangerous area of fracture. The results of temperature analysis show that the temperature of sheet metal decreases rapidly during forming process, and the lowest temperature of sheet metal is located outside the flange area when the temperature of sheet metal drops from 500 ℃ to 467  ℃ after forming. Then, the thickness distribution calculated by simulation is consistent with the experimental results, and the thicknesses of the bottom surface and the flange basically remain unchanged. Thus, thinning mainly lies in the punch, die fillet region and sidewall region, and the established thermomechanical coupling finite element model is verified to be effective for aluminum alloy hot stamping simulation.