Abstract: Numerical integration is applied for computing the far field pattern of parabolic reflector antennas.To analysis different grid forms,three improved Gaussian formulas are deduced as follows:1.Gaussian formula in polar coordinates for sectorial grid;2.Gaussian formula in area coordinates for triangle grid;3.Gaussian formula in area coordinates for quadrilateral grid.Compared with the traditional integration,formulas proposed in this paper are more accurate and less time expense;compared with the Hammer formula,formulas here are more accurate and could be used to quadrilateral elements.The influence of grid partition's forms and density on integrative precision is discussed.Results of examples are submitted to demonstrate the proposed formulae.