Microstrip slot antenna fed by microstrip line with multi tuning stubs to increase the bandwidth is proposed. The microstrip line composed of tuning stubs is used to control microstrip slot antenna real impedance to match with impedance characteristic of feeding line so that it could increase the bandwidth. The proposed antenna design achieves good input impedance in the range frequencies of 1.3 - 5.1 GHz for single antenna element, and 1.1 - 6.4 GHz for a sub array antenna composed of two antenna elements. It is shown that the measured return loss S11 agrees well with the calculated results for single antenna element. In addition, a calculation for a sub array is shown a substantial bandwidth enhancement.