In this letter, a new design of a metamaterial-based microstrip antenna is presented using triangular slots embedded on the ground plane to enhance the impedance bandwidth. To improve the impedance bandwidth of the proposed antenna, two resonant mode frequencies are closely allocated using the slotted ground without changing the radiator element. The impedance bandwidth of VSWR < 2.5 is measured at 2.43GHz (37.6%) centered on 6.46GHz, from 5.24GHz to 7.67GHz in good agreements with the simulated results.