This study investigates thermomechanical fatigue stress in turbine blades under transient thermomechanical load to propose structural optimization strategies. A numerical model of turbine blade was established using finite element analysis method. Numerical simulation of turbine blades was carried out considering the coupling effect of centrifugal mechanical load and thermal load. The spatiotemporal evolution behaviors of thermal stress and thermomechanical stress are systematically analyzed at various temperature changing rates (30–200 ℃/s) and rotational speed changing rates (300–3000 rpm/s). By optimizing the blade centroid distribution and cooling passage configuration, stress differential reductions of 50% (solid) and 53% (hollow) are respectively achieved, resulting in strengthened reserves and prolonged rupture life. A method for thermomechanical strength evaluation and structural optimization of turbine blades under transient thermomechanical loads is developed, providing a new approach for strength analysis and structural design of turbine blades for variable cycle engines.