Abstract: As key pressure-bearing components of ships and other equipment, the precise forming of thick plate large shells is a difficult point in the manufacturing field. Taking the typical segmented component of the TC4 titanium alloy thick plate large shell-the melon petal as the research object and aiming at the springback control problem during its hot pressing forming process, the hot pressing forming process was adopted to carry out for high-precision technology research. Based on the thick-direction non-uniformity characteristics of the thick plate and the high-temperature stress relaxation behavior, a hierarchical strain compensation and stress relaxation constitutive model was established. The entire process of hot formingstress relaxation-springback of the melon petal segment was simulated by using Abaqus software. The simulation results demonstrate that under forming temperature of 850 ℃, strain rate of 0.01 s^-1, and the stress relaxation holding time of 900 s,the shape tolerance of the melon petal segment is controlled within ±2 mm, successfully addressing the precision forming difficulties of TC4 thick plate large shell. And trial production of the melon petal was carried out, it is found that the overall trend of the finite element simulation results is consistent with the test results, verifying the feasibility and accuracy of the finite element simulation.