The invention discloses a method for preparing a flexible thermosensitive film material. According to the method, MnCO3 powder, Co2O3 powder, Ni2O3 powder are used as raw materials and subjected to grinding, screening, synthesizing, fine grinding, pre-molding forming and sintering under the oxygen-enriched atmosphere to be made into a ceramic target, a polyethylene glycol terephthalate sheet and a polyimide sheet are used as substrates, and an MCNO film is deposited at the room temperature in a sputtered mode through a radio frequency magnetron sputtering method. The method has the advantages that firstly, sputter deposition is completed at the room temperature, and the purpose of depositing the MCNO thermosensitive film on the polyethylene glycol terephthalate substrate, the polyimide substrate and other organic flexible substrates is achieved; secondly, the MCNO film prepared through the method is low in specific resistance, and the negative temperature resistance coefficient is high, so that responsivity of elements is better increased, and noise of the elements is better lowered; thirdly, preparation is conducted at the normal temperature, high-temperature heat treatment is not needed, energy consumption is low, energy is saved, and the environment is protected; and fourthly, the sputter deposition temperature is low, the method is easily compatible with a Si-based semiconductor process, and the thermosensitive elements can be directly prepared on Si-based reading circuit chips, so that the cost for preparing thermosensitive type uncooled infrared focal plane arrays is greatly lowered.