Based on surface plasmon resonance (SPR) and coupled mode theory (CMT), the formation mechanism of double Fano resonances is studied in a hybrid sensing structure composed of subwavelength dielectric grating/metal-dielectric-metal (MDM) waveguide/periodic photonic crystal. Studies show that the dynamically adjustable double discrete states generated in the subwavelength dielectric grating and MDM waveguide are coupled with the continuous state formed in the periodic photonic crystal respectively to achieve double Fano resonances. And the double Fano resonances can be dynamically modulated under the angular modulation by the structure parameters. Surprisingly, the figure of merit (FOM) value of 4.00 x 104 is also achieved, which demonstrates the proposed structure has potential applications in sensing. In addition, the low and high refractive index sensing regions are set up. Simultaneous detection of refractive index ranges 1.00-1.29 and 3.79-4.14 is achieved. Thus, the proposed structure provides an effective reference for studying the dynamic modulation of double Fano resonances and high throughput sensors.