Abstract: To cover terrestrial trunked radio(TETRA)communication of 800 MHz band and wireless local area network(WLAN) of 5 GHz band, a new fourelement dual-mode antenna is designed based on the aperture-sharing technology and the multiple-input multiple-output(MIMO)technology. WLAN band element are used the stacked structure and MIMO technique to increase the communication capacity.TETRA band element is used the air microstrip antenna and excited fed by a coupling circle patchwhich sharing aperture with WLAN elements to realize the compact struture.The simulated and measured results show that the TETRA element impedance bandwidth(VSWR less than 2)is 806-866 MHz and the gains are over 6 dBi; while the WLAN element impedance bandwidth is 4.9-6.1 GHz the gains are over 8 dBi.The port isolations are over 22 dB at both bands, furthermore, envelope correlation coefficients(ECCs)are less than 0.01 which satisfies the MIMO antenna standard.