In order to explore effect of structure on the temperature sensitivity of partially carbonized carbon fibers, different heat treatment temperatures (700, 750 and 800 °C) and heat treatment times (3 and 9 min) were used to prepare fibers with different structures. The electrical resistivities were monitored whilst the room temperature was increased from 30 to 100 °C, which was used to characterize the temperature sensitivity. The fibers showed negative temperature coefficients in the temperature range. Infrared spectra, an element analysis, a scanning electron microscope (SEM), Raman spectroscopy and X-ray diffraction measurements were used to study the microstructure of the fibers. Through the analysis, the proportions of the graphite-like structure, graphitization degree and size of the graphite-like structure crystallite influenced the temperature sensitivity. The main electron transfer method used for the fibers was variable-range hopping. This indicated that the fibers had a potential application of preparing thermistors in polymer composites.