On the basis of the method of moments and segments sinusoidal basis functions, the impedance matrix of plasmonic nano-rod antennas can be obtained by solving the Green′s function of the discretized current nodes in closed form formulations. Compared to the method of moments with different basis functions, this method can be utilized for reducing the size of matrix equations. The simulated results show that the polarization current and scattered fields can be computed accurately by employing a small-size matrix, which leads to a fast analysis for the scattering characteristic and resonant modes of nano-rod. The accuracy of the method was successfully demonstrated by comparing the simulated results with finite difference time domain technique, which is more time-consuming than the present method. Especially when dealing with the oblique incidence problem, the advantages become more apparently. The method is effective for the calculated models in this paper, and provides a fast and efficient electromagnetic analysis way for other nano-rod antennas and nanotube devices in different shapes when doing their scattering characteristics simulation.