<p>This paper proposes an isogeometric shape optimization method for elastic metamaterial plates under temperature rise, aimed at maximizing band gaps. An isogeometric model of the motion equations for metamaterial plates under temperature rise is constructed to compute the band gaps. An optimization framework is established by defining the band gap as the objective function and using the coordinates of NURBS control points as design variables. The optimization problem is solved using the particle swarm optimization (PSO) algorithm. A boundary optimization strategy based on control point selection is developed to systematically adjust the interfaces of both bi-material and tri-material metamaterials. Furthermore, the temperature rise is introduced via nonlinear membrane strain, which modifies the stiffness matrix and thereby influences band gap characteristics. Numerical examples are provided to validate the effectiveness of the isogeometric model. The numerical results demonstrate that the boundary optimization strategy enables smooth shape evolution during the optimization process and effectively maximizes the band gaps of both bi-material and tri-material metamaterials. Additionally, the effect of temperature rise on the optimized structure and corresponding band gap is investigated.</p>