Abstract: The biological behavior of carbon dots, especially the mechanism of cellular uptake and intracellular distribution, is the basis of its biomedical applications. In this paper, blue fluorescent carbon quantum dots were synthesized by hydrothermal method with Poria cocos polysaccharide as raw material, and the specific biological behavior of carbon dots entering cells was explored to evaluate its biological activity. It was characterized by transmission electron microscopy, UV-vis absorption spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Two different cell lines, immunocytes-RAW264.7 cells (mouse mononuclear macrophages cells) and cancer cells-4T₁ cells (mouse breast cancer cells), were used as the research objects to study the uptake kinetics, uptake pathway, distribution and efflux of polysaccharide carbon dots in cells. The results showed that the carbon dots have a size distribution of 2 to 10 nm, and the average size was 6.85 nm. The carbon dots were mainly composed of C, O and N elements, with abundant surface functional groups such as -OH, C=O, C-N and C=C, and the fluorescence quantum yield was 4.72%. Carbon dots enter cells in a certain concentration and time dependence. Different cell lines have different uptake pathways. RAW264.7 cells enter the cells mainly by macrophage-specific phagocytosis, and a small part of the endocytosis is mediated by caveolin, while 4T₁ cells are mainly mediated by grid protein endocytosis and giant cell drinking process. In summary, the synthesized carbon dots have good fluorescence properties, low cytotoxicity and excellent biocompatibility, which can be used for cell imaging applications.