NOVELTY - Preparing thermochromic sensing material comprises: dissolving the diacetylene compounds by using the organic solvent, obtaining diacetylene compound solution; and then uniformly mixing the polydimethylsiloxane, curing agent and diacetylene compound solution and obtaining mixture solution.    USE - The method is useful for preparing thermochromic sensing material (claimed).    ADVANTAGE - The preparation method of the thermochromic sensing material has simple operation, low cost, is convenient to carry, controllable shape of the thermochromic sensing material and good elasticity; it can be widely applied to the field such as sensors, organic photoelectric device.    DETAILED DESCRIPTION - Preparing thermochromic sensing material comprises: dissolving the diacetylene compounds by using the organic solvent, obtaining diacetylene compound solution; and then uniformly mixing the polydimethylsiloxane, curing agent and diacetylene compound solution and obtaining mixture solution, where the content of the diacetylene compound in the mixture solution is 0.05wt%-0.2wt%, and the rest is polydimethylsiloxane and curing agent; the weight ratio of polydimethylsiloxane to the curing agent is 15:1-5:1; and then decompression removing the organic solvent in the mixture solution, curing the mixture at 20-80 degrees C, lighting the cured substance for 5-300 seconds in the 254nm ultraviolet lamp, making the diacetylene compound generate polymerization to generate polydiacetylene, obtaining blue solid thermochromic sensing material; or dissolving the diacetylene compounds by using the organic solvent, obtaining diacetylene compound solution; and then uniformly mixing the polydimethylsiloxane and diacetylene compound solution and obtaining mixture solution, where the content of the diacetylene compound in the mixture solution is 0.05wt%-0.2wt%, and the rest is polydimethylsiloxane; and then decompression removing the organic solvent in the mixture solution, lighting the mixture without organic solvent for 5-300 seconds in the 254nm ultraviolet lamp, making diacetylene compound generate polymerization to generate polydiacetylene, obtaining blue solid thermochromic sensing material.