Based on coupling mode theory,microring resonant theory and electro-optical mod ulation theory, we propose an electro-optically tunable microring resonator with two U-bend wa veguides.The relationships between output spectrum and the length of U-bend waveguide as well as coupling coefficient are analyzed through simulation.The simulation results show that the 15μm radius microring outputs a relatively large free spectrum range of 56nm,a 60dB higher extinction ratio and an extremely na rrow bandwidth when the coupling coefficient is locked in a very reasonable range.Besides,the output wav ele ngth and extinction ration can be modulated by the voltages loaded on microring and U-bend waveguide respe ctively.