Abstract: The method of moments (MOM) is usually used to solve the electromagnetic scattering problems. When the number of unknowns is increasing, the memory and computation time consumed becomes insufferable. In this paper, the best uniform approximation theory is used to construct a high-order method of moments, and the Compute Unified Device Architecture (CUDA) technology based on graphics processor unit (GPU) is introduced to achieve parallel speed up two-dimensional electromagnetic scattering problems. Numerical results show that compared with the FMM, the proposed method has higher accuracy with lower discretization, and the speed of impedance matrix filling and moment vector multiply is greatly improved, which can be used as an efficient tool to solving the scattering problems of the electrically large targets.antenna is fed by a modified Marchand balun to achieve broadband operation in UHF band. Several Ushaped slots are cut in the ground plane of the conventional balun to change the capacitance between coupled line and the ground plane, which can achieve a high ratio of even mode to odd mode impedance and a broadband operation. The impedance bandwidth determined from a 10dB return loss is found to be about 40%, with the bandwidth 530MHz to 790MHz.The antenna has been fabricated,measured and simulated results are in close agreement. The antenna is particularly useful in the low microwave frequency band.