A compact dual-band planar monopole antenna for 2.4/5GHz WLAN application is presented. The two resonant modes of the proposed antenna are associate with four slots which contribute to the upper resonant frequency and can reduce the size of the lower resonant length. The parametric study is performed to understand the characteristics of the proposed antenna. Experimental results show that the designed antenna can provide excellent performance for 2.4/5GHz WLAN system, including sufficiently wide frequency band, moderate gain, and nearly omnidirectional radiation coverage.