Hexavalent chromium (Cr(VI)) is a well known toxic carcinogens.Therefore, the convenient and quick detection of Cr(VI) in the environment is highly desired .In this study, a new method for determination of Cr(VI) was developed based on its quenching effect on the fluorescent of carbon quantum dot (C-dots).The fluorescent C-dots with strong photoluminescence and high photostability were prepared via a low cost, facile one-step hydrothermal approach from ammonium citrate.The C-dots probe shows many obvious advantages of convenience and simplicity.The C-dots-based sensor has highly selectivity and sensitive for Cr(VI) in a wide concentration range of 0-50 μM.The detection limitation comes to 0.015 µM .