In this study, a time-jerk optimal trajectory optimization method based on a multistrategy improved whale optimization algorithm and particle swarm optimization (MIWOA-PSO) is proposed for enhancing the working efficiency of the segment erector in shield tunneling, reducing motion impact during segment assembly, and improving operational stability. Firstly, kinematic analysis of the segment erector is conducted, and the target trajectory in Cartesian space is mapped to the joint space via inverse kinematics solutions. Secondly, the segment assembly path is interpolated using quintic non-uniform rational B-spline (NURBS) curves, and an objective function with time and jerk as the optimization targets is established. Concurrently, the performance of the whale optimization algorithm (WOA) is optimized via multistrategy improvements: Tent chaotic mapping is employed to increase the population diversity, mutation operations from the genetic algorithm are introduced to enhance the global search capability, and an elite opposition-based learning strategy is incorporated to prevent premature convergence. The improved WOA is then hybridized with the PSO algorithm to form the MIWOA-PSO algorithm. Finally, an initial smooth trajectory is generated using quintic NURBS, and the time parameters are optimized via the MIWOA-PSO algorithm to derive a time-jerk optimal motion profile. The results indicate that: (1) in terms of operation time, the total duration of the optimized trajectory is 23.23 s, which is 4.77 s (17.04%) shorter than the pre-optimization time of 28 s, indicating improved operational efficiency of the segment erector; (2) regarding motion smoothness, the jerk in each joint is effectively suppressed, where the maximum joint jerk is only 33.58% of the limit, indicating enhanced operational stability of the segment erector.