首先推导出波导探针输入阻抗的一般变分表达式。通过对介质加载波导的并矢格林函数求解，得到了矩形波导中截面探针输入阻抗的积分表达式。该表达式可直接作为分析微带探针或对探针进行优化的依据。利用之中的方法对Ｋａ频段的波导截面探针进行宽带优化设计，经实验验证，得到低插损、小驻波的波导——微带转换结构。 First, we derive the general variational expression of waveguide probe’s input impedance. By solving the dyadic Green’s function of the dielectric loading waveguide, the integral expression of the input impedance of the cross-section probe in the rectangular waveguide is obtained. This expression can be directly used as a basis for analyzing microstrip probes or optimizing probes. By using the method, a broadband optimization design of the waveguide cross-section probe in the Ka-band is carried out. The waveguide-microstrip conversion structure with low insertion loss and small standing wave is obtained through experiments.