A simple ratiometric fluorescence system was designed for rapid, sensitive and visual detection of the Hg2+ content in camellia oil. The system was composed of cadmium telluride quantum dots (Cd/Te QDs) with red fluorescence and camellia oil naturally with blue fluorescence, and can detect and analyze the Hg2+ content in camellia oil (as low as 6.04 nM). Appropriate adjustment of fluorescence intensity ratio made the fluorescence of the sensor system turn pink. The red fluorescence of CdTe QDs in the system was quenched due to the charge transfer upon the addition of Hg2+. With the increase of the Hg2+ concentration, the color of the system exhibited significant color change (from pink color to blue color). In order to evaluate the selectivity of the ratio fluorescence system towards Hg2+, different metal ions were added to the ratiometric fluorescence system under the same conditions did not change the fluorescence intensity and color of the system. Further addition of 200 nM of Hg2+ decreased greatly the fluorescence intensity ratio (I677/I431) of the system and changed significantly the fluorescence color. These results indicated that thus this system exhibited strong anti-interference ability and could meet the detection requirements of actual samples. The simple method is fast, sensitive and inexpensive, and provides a new strategy for rapid detection of heavy metal ions in camellia oil.