This paper proposed a pattern diversity antenna. It is proposed for 2.4GHz ISM band wireless LAN system. The antenna structure is based on a half-wavelength square printed antenna. The RF switches are installed on each side of the antenna to perform switched-beam in order to accomplish the pattern diversity. The characteristics of the antenna are evaluated and presented in this paper. The radiation pattern and directivity of the antenna are calculated by using the finite-difference time-domain(FDTD)method. The diversity characteristics, L.e., correlation coefficient and diversity gain of the antenna are also evaluated. The antenna is investigated for optimum characteristics for wireless LAN application. The numerical results show the greater than 0dBi of antenna directivity and the radiation patterns with the correlation coefficient of 0.5, which can provide the diversity performance. Also, the diversity gain of 8dB at 1% probability can be obtained with the switched combining technique. In addition, the experiment is carried out to verify the characteristics and performance of the antenna. The experimental results show agreement with the numerical result.