The thermal characteristics of bearing rotating elements are essential for the service evaluation of bearing. However, the existing monitoring methods are limited by bearing internal complex structure and extreme operating environment. Hence, based on the monitoring technology of CdTe quantum dots (QDs) sensor, an improved QDs sensor was fabricated by process optimization and polymers coating, which enables bearing rotating elements thermal monitoring for extreme working condition. First, the principle of the measurement was introduced and the existing problems were analyzed. Then, the influence of preparation process on temperature-dependent photoluminescence (PL) spectra of CdTe QDs was investigated. The performance improvement methods of the QDs sensor, both organic coating and inorganic coating, were investigated. The fabricated sensor named CdTe@PVA presents remarkable improved performance in fluorescence intensity, highest tolerable temperature and stability. In the end, a rolling bearing experimental rig was set up and the temperature of the bearing cage at different rotation speeds were captured by using the proposed CdTe@PVA sensor.