Abstract: In terms of the limitations of small range and insufficient flexibility of the traditional flexible photonic crystals, a novel flexible photonic crystal with a triangular lattice of two-dimensional air-column nanostructures was designed and fabricated via nano-imprinting technology. The mechanochromic properties and operational stability of the proposed photonic crystal were systematically investigated using various experimental techniques, and its potential applications in strain sensing and dynamic display were explored. Results indicate that under uniaxial stretching, the sample exhibits a continuous blue shift in color with increasing strain, achieving a bandgap center wavelength shift of 180 nm—covering the entire visible spectrum. Moreover, the material demonstrates excellent stability over 2,000 cycles of repeated stretching. The proposed flexible photonic crystal combines a broad color-change range with high sensitivity to small strains, overcoming the limitations of traditional strain sensors. This innovation holds promise for applications in visual strain monitoring and dynamic display systems.