The present invention provides a wideband frequency tunable ring resonator, wherein, comprises a closed λg/2 transmission line and two variable capacitors with tunable capacitance, the λg/2 transmission line is axisymmetric around a central line, first ends of the two variable capacitors are respectively connected to two intersection points of the λg/2 transmission line and the central line, the second ends of the two variable capacitors are respectively grounded. By implementing the technical solution of present invention, following technical effects are obtained. The fundamental resonant frequency (ffund) can be shifted up and down by controlling the respective values of the two loading capacitors, resulting in a bi-directional tuning of ffund. As a result, the tuning range of this invention can be approximately doubled as compared with the conventional tunable ring resonator.