The invention relates to the field of a carbon nano material, and provides a nitrogen-doped fluorescent carbon-dot and a carbon-dot graphene composite as well as a production method and an application thereof. The nitrogen-doped fluorescent carbon dot is characterized in that the nitrogen element exists in the form of pyridine nitrogen, pyrrole nitrogen and graphitic nitrogen; the nitrogen atom and carbon atom are in a molar ratio of 0.035 to 0.057; the average granularity is 2.5nm to 4.1nm. The invention also provides a preparation method of a fluorescent carbon dot. The preparation method comprises the following steps: (1) carbonizing coal with high content of nitrogen to obtain a carbonized material, wherein the coal with high nitrogen content refers to the coal with the nitrogen content of 1.1 to 3.0 percent; (2) producing an anode through the obtained carbonized material, and electrochemically oxidizing the anode to obtain the fluorescent carbon dot. The invention also provides a carbon-dot-graphene composite material prepared through the nitrogen-doped fluorescent carbon dot. In addition, the invention also provides an application of the fluorescent carbon dot in the fields such as photoelectric devices, biological imaging, oxidation-reduction electric catalyst, detection and sensing and an application of an oxidation-reduction electrochemical catalyst in the field of a fuel battery.