本文从菲涅尔-基尔霍夫衍射公式出发，结合贝塞耳函数等特殊函数的性质，计算了正入射高斯光束圆孔衍射的光强分布，并以洛默尔函数的形式表示了焦点附近的光强分布. 之后选取了几何焦平面、光轴以及几何阴影区域边界这三个特殊区域，理论结合数值方法给出了光强分布的解析表达式以及数值结果，并发现高斯光束束腰半径越小，艾里斑半径越大，同时焦深也越大. 最后计算了焦平面上的光强积分强度,结果表明束腰半径越小，光强就越向中心集中. 同时高斯光束相较于平面波的衍射，不会改变光强分布的整体轮廓，但会使得光强向焦点处集中.

Based on the far-field Fresnel Kirchhoff diffraction formula and combined with the properties of Bessel function and other special functions,the diffraction intensity distribution of a circular aperture with normal incidence Gaussian beam is calculated. The intensity distribution near the focus is expressed in the form of Lommel function. Then three special regions,namely geometric focal plane,optical axis and geometric shadow region boundary,are selected,and the analytical expression and numerical results of light intensity distribution are given theoretically and numerically. It is found that the smaller the waist radius of Gaussian beam,the larger the radius of the Airy spot,and the greater the focal depth.Finally,the integral intensity of light intensity on the focal plane is calculated. The result indicates that the smaller the waist radius is,the more concentrated the light intensity is to the center. Compared with the diffraction of plane wave,the Gaussian beam will not change the overall contour of the light intensity distribution,but will make the light intensity concentrate to the focus.