In this letter, we report a flexible, all-dielectric metasurface fabricated via nanosphere lithography (NSL) and demonstrate its potentials in sensing applications. Regularly arrayed Si cylinders with hexagonal lattice fabricated on polyethylene terephthalate (PET) flexible substrate are exploited to detect applied strain and surface dielectric environment by measuring transmission spectra. Further numerical simulations coincide with experimental observations. The transmission peak can be attributed to coupled magnetic Mie resonance between close-packed Si cylinders. Such Mie resonance based sensor with high flexibility offers an alternative approach towards detecting surrounding variations besides traditional plasmon resonance based sensors, and provides more choices for designing photonic devices operating in the optical regime.