Abstract: The design method of impedance matching for planar slot antenna is discussed in this paper. The impedance matching criterion that the sum of all the radiating s lot normalized conductances is equal to 2 for the inner feed, and also the sum o f all the coupling slot normalized impedances for the series-shunt inner feeder is equal to 2 are verified by using microwave network theory. According to this method , a new matching criterion of coupling slots is derived for the series- series feeder and the shunt-series feeder.