In order to let students master how to use fluorescence spectrophotometer, and how to apply fluorescence sensor on food additives quantitative analysis, a research-oriented synthetical experiment has been designed. Based on fluorescence quenching effect of food additive Ponceau 4R on the fluorescence emission intensity of graphene quantum dots(GQDs), and the effect of pH and incubation time on this quenching reaction, relationship curve between concentrations of Ponceau 4R and variety of fluorescence emission intensity of graphene quantum dots was obtained, furthermore the concentration of Ponceau 4R in beverage was analyzed. Reaction mechanism has been introduced into the experiment process, which not only can wide knowledge of students, but also can improve their ability of solving practical problems. This interesting scientific experiment could encourage and waken study interest of students. And this experiment is simple, easy and suitable for undergraduate's synthetical experiment capability training.