Abstract: Based on electromagnetic theory, the analytical and numerical results of radial energy of linear element planar antenna array excited by electromagnetic pulse are offered at first, then, by analyzing the results with the interference and the diffraction theories, following conclusions are got: (1) The electromagnetic radiation problem of plane linear element planar antenna array can be solved by grating equation concisely. (2) The maximum energy of bounded beam is proportional to the square of the number of element of antenna array. (3) Keeping the same line elements of antenna array feeding at the same time while each row successive postpone properly, the beam can be restrained within the expected area. (4) The effective scanning angle range depends on the given half angle width.