We propose a novel, to the best of our knowledge, sensor for nanovibration detection based on a microsphere. The sensor consists of a stretched single-mode fiber and a 2 µm microsphere. The light from the optical fiber passes through the microsphere, forming a photonic nanojet (PNJ) phenomenon at the front of the microsphere. The evanescent field in the PNJ enhances the light reflected from the measured object to the single-mode fiber-microsphere probe (SMFMP). Results showed that the system can detect arbitrary nanovibration waveforms in real time with an SMFMP detection resolution of 1 nm. The voltage signal received and the vibration amplitude showed a good linear relationship within the range of 0-100 nm, with a sensitivity of 0.7 mV/nm and a linearity of more than 99%. The sensor is expected to have potential applications in the field of cell nanovibration detection.