In this paper, an optimization technique combining non-conformal integral equation domain decomposition method (IE-DDM) and particle swarm optimization (PSO) is presented for the design of antenna on platform. The antenna and the platform can be decomposed into different closed sub-domains according to design requirements and the DDM is used to compute the scattering from antenna on platform. Meanwhile PSO is used to find the best antenna location. Numerical example is presented to demonstrate the efficiency of the present method.