The filter characteristics of the through port in single-ring and double-ring resonators based on silicon-on-insulator were researched, and the influence of the coupling coefficient between the straight-ring waveguide and the coupling coefficient between the ring waveguides on output characteristics were analyzed. An improved coupling structure using the Mach-Zehnder interferometer (MZI) in the coupling region of the resonator was proposed. In the single-ring and double-ring filters with a microring cavity length of 1 218 μm, the resonators were tuned from under-coupled state to the critical-coupled state in the power range of 19 mW and 9 mW, respectively. Moreover, the filter profile of the double-ring filter was tuned for one free spectrum range (FSR) when the heating power was 26 mW.