The FDTD method modeled the micro-slotline leaky wave antenna successfully.The traveling wave of micro-slotline leaky-wave antenna in leaky region had been shown up with FDTD method.A new and effective equation was proposed

to calculate the complex propagation constant of micro-slotline leaky wave antenna.The numerical result calculated by the new and efficient method agrees well with measured results and comparing data.Based on the model of FDTD and the novel equation

the character of micro-slotline leaky wave antenna is shown up.The numerical result points out that the width of micro-slotline leaky-wave antenna affect character of antenna.Based on it

that is a new way to make main lode scan at fix-frequency.