In Isogeometric boundary element method（IGA-BEM）, Non-Uniform Rational B-Splines（NURBS） which are used for describing the geometric boundary in a computer-aided geometric design（CAGD） are employed as shape functions of Boundary Element Method. IGA-BEM not only can accurately describe the geometric boundary, but also unify the design model, analysis model and optimization model, so it can avoid the repeated meshing and mesh distortion problems in the optimization process and it also can improve the efficiency of the design, calculation and optimization. In this article IGA-BEM is combined with particle swarm optimization（PSO） to study the shape optimization of two-dimensional linear elastic structure. Compared with the gradient-based optimization algorithms, gradient-free PSO algorithm can avoid the complicated sensitivity analysis process and make the optimization process easier. The efficiency and accuracy of the combined isogeometric boundary element method-PSO are demonstrated through two shape optimization examples.