ABSTRACT In this work, the reinforcement design and optimization method integrating the superelement model and equivalent static load method (ESLM) is proposed for the lower impact region of carbon fiber‐reinforced thermoplastic composite (CFRTP) B‐pillars for automobiles. First, the validity of the B‐pillar finite element model (FEM) is verified through comparison with drop‐weight impact test data from the metal B‐pillar. A layer stacking scheme suitable for the load‐bearing condition of the B‐pillar is proposed, highlighting its advantages in weight reduction and impact resistance. Subsequently, the grid stiffeners suitable for B‐pillar geometry are designed to improve the stiffness of the collision‐prone lower region. The customized superelement model and ESLM are employed to condense the CFRTP B‐pillar model, improving computational efficiency. The grid stiffener layout parameters and thickness suitable for the CFRTP B‐pillar are provided by a high‐precision RBF surrogate model. Results indicate that the optimized stiffener configuration reduces the maximum intrusion displacement at the critical node by 39% compared to the CFRTP B‐pillar without reinforcement. This study contributes to enhancing the structural stiffness of composite B‐pillars and offers an effective solution for achieving lightweight and impact‐resistant structural design.