A series of facile flexible reversible thermochromic membranes containing micro/nanoencapsulated phase change materials were fabricated, which presented excellent thermochromic performance and striking latent heat storage property. In this composite membrane, the polyvinyl alcohol/water-soluble polyurethane composite was served as polymer matrix material, and the reversible thermochromic micro/nanoencapsulated phase change materials (TC-M/NPCMs) which energy storage efficiency reached 67.5%, were served as functional fillers. Moreover, trimesoyl chloride was used for modifying the water resistance of thermochromic membranes. The effects of TC-M/NPCMs contents on the morphology, thermochromic performance, thermal property, thermal stability and thermal cyclic durability of flexible thermochromic membranes were experimentally investigated using field-emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), digital camera, differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA), et al. The results revealed that TC-M/NPCMs were distributed evenly in matrix membranes. The color of these obtained flexible thermochromic membranes could change in response to variation of external ambient temperature and thus presenting perfect thermochromic performance. As TC-M/NPCMs content increased, the mechanical property and thermal stability of membranes declined, while the enthalpy raised. In addition, the static water contact angles (WCAs) analysis indicated that the water resistance enhanced greatly after surface modification. Furthermore, thermochromic membranes still exhibited worth mentioning thermal cyclic durability undergoing 100 heating and cooling cycles. A facile temperature colorimeter was designed and fabricated, by using the flexible thermochromic membrane with heat storage and temperature regulation property, which could be served as a promising wearable temperature sensor. Hence, the application of the prepared thermochromic membrane in thermal regulation, energy storage and wearable temperature sensor has great potential in the future.