The carbon dots have got much attention recently. Considering the environment protection, "green" materials are urgent. In this paper, nitrogen-and sulfur-co-doped carbon dots (N, S-CDs) were prepared through one-pot simple and convenient hydrothermal carbonization approach with "green" ginkgo leaves as the materials. The synthesized carbon dots were successfully doped with nitrogen and sulfur elements. The fluorescence intensities of carbon dots were rather stable in different pH and ionic strength. Furthermore, the "green" N, S-CDs were successfully applied in bioimaging as fluorescent probes due to its excellent optical properties and low cytotoxicity. (C) 2017 Elsevier B. V. All rights reserved.