Abstract: In this article,a calculation method of convolution integration for near field diffraction of aperture antennas is discussed.This method can accomplish fast calculation by FFT,and it is a more efficient one than direct integration or spherical wave expansion method(SWE).Based on this,the properties of the near field diffraction of typical circular and rectangular aperture antenna are discussed, and the results analysis show that the distribution of diffraction field amplitude and phase as closely related to the shape,size of aperture and distance from observation plane to the aperture.At the end of this paper,problem about how reduce near field diffraction of aperture are discussed.