When an electric or magnetic line source is located in the presence of semi-elliptical cylnder, far field pattern is analyzed by hybrid UTD (Uniform Geometric Theory of Diffraction)-MM(Moment Method) technique developed in this thesis. By reciprocity theorem and UTD, the known currents are obtained. The basis function for unknown current in the smooth convex region of the scatterer is assumed and used in solving problem by MM method. Because of reduced number of basis function employed in the present method, the computing time is considerably reduced in the analysis of large scatterers. Whereas UTD solution is invalid in grazing incidence case, this hybrid method, can be applied in that case, also. Numerical results are compared with MM results and proved to be accurate considerably.