In response to the problems of overly large size，insufficient adjustable frequency range， narrow bandwidth and difficulty in covering 5G/WiMAX/WLAN and other common frequency bands， this paper proposes a novel structure of frequency reconfigurable antenna with three operating states， which can work in the above frequency bands respectively. The size of the antenna is only 26 mm×32 mm×1 mm， which makes it more suitable for small mobile communication devices. The antenna is designed to switch between different modes of antenna operation by combining a new radiating patch element with slotting and switching. The antenna consists of two parts： microstrip patch antenna and DC bias circuit. The DC bias circuit consists of two sets of switches SW1 and SW2 consisting of four diodes and DC bias lines. By controlling SW1 and SW2， the antenna can work in broadband and two dual-band states. The broadband operating bands are 3.04~5.54 GHz. One dual-band operating bands ranges between 2.86~3.50 GHz and 5.09~6.17 GHz，and another dual-band operating bands ranges between 2.98~3.84 GHz and 4.61~5.88 GHz. The antenna model is physically processed and measured. The optimization test shows that the antenna can work normally in broadband mode and two dual-band operating modes， and the reconfigurable characteristics of the antenna enable it to switch operating modes in different communication bands of 5G/WiMAX/WLAN， which is ideal for complex communication environments where 5G/WiMAX/WLAN sources are aggregated.