A CPW-fed quaternary ultra-wideband (UWB) high isolation antenna based on FR4 is proposed in this paper. The antenna consists of four cell slot antennas with overall size of 65 mm×65 mm×0.8 mm. The ultra-wideband characteristics of the antenna are achieved through the use of defective ground structures and corner cuts. The unit antennas are placed vertically to each other to achieve polarization diversity, at the same time; an isolation fence structure is loaded in the middle of the antenna, which greatly increases the isolation of the antenna. The antenna was fabricated and tested. The test results show that the proposed antenna can cover the frequency of 2.86-11.1 GHz and the isolation is greater than 20 dB in the band. It has the characteristics of high isolation, ultra-wideband and low envelope correlation coefficient (ECC<0. 006). The antenna adopts the CPW feeding, which is easier to apply in integrated circuits and suitable for various ultra-wideband systems.