The semiconductor nanocrystal quantum dots (QDs) have excellent photo-physical properties, and the QDs-based probes have achieved encouraging developments in cellular and in vivo molecular imaging. More and more researches showed that QDs-based technology may become a promising approach in cancer research. In this review, we focus on recent application of QDs in cancer diagnosis and treatment, including early detection of primary tumor such as ovarian cancer, breast cancer, prostate cancer and pancreatic cancer, as well as regional lymph nodes and distant metastases. With the development of QDs synthesis and modification, the effect of QDs on tumor metastasis investigation will become more and more important in the future.