The purpose of this study was to explore the haemostatic effect of novel carbon dots (CDs) derived from Cirsii Japonici Herba Carbonisata (CJHC). Transmission electron microscopy (TEM), high-resolution TEM, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy, high performance liquid chromatography and a cell counting kit-8 assay of CJHC-CDs were performed. Then the haemostatic effect of this CJHC-CDs was studied in bleeding mouse models. To explore their related haemostatic mechanism, coagulation parameters and platelets (PLT) were measured. The CJHC-CDs ranged in diameter from 2 to 11 nm and had a quantum yield of 0.63%. They exhibited no toxicity up to concentrations of 5752 μg/mL. After administration, mice had a significantly shortened bleeding time and the coagulation parameters and PLT significantly increased. These results showed the definite haemostatic effect of CJHC-CDs.