One of the major challenges in realizing all-optical switching is urgent demand for dense integration and high extinction ratio (ER). In this paper, all-optical switching in silicon-on-insulator (SOI) serially coupled double-ring resonator based on thermal nonlinear effect is proposed. The radii of double ring resonator are both 10 μm. Theoretically, switching ER is improved at the same resonance wavelength of serially coupled double-ring resonator. Then, basic characteristics of all-optical switching in serially coupled double-ring resonator based on thermal nonlinear effect are researched. In experiments, firstly measured by single pump injection technology with easily coupling surface grating coupler method, the highest notch of serially coupled double-ring resonator is 27 dB. And the highest ER is 20.2 dB based on thermal nonlinear effect by adjusting the power of injected light. The slope of resonant wavelength as a function of injected pump is 136.4 pm/mW. Secondly, switching time measured by two pump injection technology is 2.84 μs and 3.04 μs, respectively. The results which are in agreement with theory between single and two-pump-injection technology are compared and analyzed. Those provide efficient method for optical router and modulation with dense integration and high performance.