An extreme wideband eccentric annular slot antenna is designed. Its structure is simple. This antenna is analyzed and optimized by using the IE3D software. The eccentric annular slot and coupled microstrip feed-line are built on the FR4 printed board. The prototype are fabricated and measured. The input impedance bandwidth is 120% for the S11<-10dB, and the operational frequency is from 2GHz to 8GHz. The antenna peak gain is 3.5dBi. This antenna can be used in the WLAN applications.