Tumor markers have been of vital importance in cancer diagnosis, treatment and monitoring. However, the sensitivity of current tumor markers for early diagnosis is low, reducing the clinical usefulness of tumor markers. Quantum dots are new fluorescent nanoparticles with unique photophysical and chemical properties, thus having a great potential impact on the investigation of cancer pathogenesis, early diagnosis, targeted therapy, prognosis and monitoring, when combined with tumor markers. The current research is focused on the detection of specific tumor markers or molecules based on tangible carriers such as cells and tissues. One of the most promising clinical applications would be to explore the potential of this highly sensitive labeling technique for the detecting and imagining tumor markers in serum and other body fluids, where some progresses have already been made recently. How to detect early cancer based solely on invisible carriers would be the next step of quantum dots bio-probes in clinical use, so as to develop a new detection technique with greater sensitivity, specificity,rapidity and availability.