The need for temperature observation appears in all aspects of our lives. With the development of science and technology, higher requirements are put forward for the combination of high-accuracy and wide detection range of the sensor. In this study, a facile strategy method was developed to prepare a NiO slurry and realize a wide-range and high-precision thermistor based on NiO. By dispersing NiO nanoparticles in polyimide (PI) to afford the NiO slurry, a thermistor was obtained by spin coating, thermal curing, and electrode preparation, which can operate in a very wide range from 220 K to 470 K, as well as exhibited an out-standing thermal sensitivity (B) with a value exceeding 5400 K. Moreover, the sensor shows very high detection accuracy and can detect small temperature differences up to 0.05 K. Notably, through brushing the mixture onto the PI substrate or peeling off from the substrate, a flexible, or freestand sensor was obtained, which displayed great mechanical properties and stabilities. This allows the sensor to be used on various curved surfaces and other objects with complex shapes, which greatly increases potential applications and the scope of the temperature sensor.