The traditional detection method of water content testing, Karl Fischer titration, cannot be widely implemented due to the inconvenience of requiring professional instruments and operators. Carbon dots are photoluminescent zero-dimensional carbon nanomaterials with sizes between 1 and 10 nm. Since the luminescence of carbon dots is easily affected by solvents, researchers have used the fluorescence intensity, emission peak position, and visible color changes to the naked eye of the carbon dots to quantify the water content within the organic solvent, but often the detection range is narrow and sometimes segmented fitting is required. These shortcomings mean that the experiments need to be further optimized. The green fluorescent carbon dots herein were prepared by hydrothermal method using citric acid and urea as precursors, and characterized and analyzed by transmission electron microscopy, UV-vis absorption spectroscopy, fluorescence spectroscopy and time-resolved fluorescence spectroscopy. The particle size of carbon dots is 6.5 nm, and there are absorption peaks at 252 nm, 273 nm, and 410 nm. The optimal excitation and emission wavelengths are 400 nm and 517 nm, respectively. It is presumed that the fluorescence of carbon dots mainly originates from the green fluorescent molecule 4-hydroxy-1H-pyrrolo [3,4-c] pyridine-1,3,6 (2H, 5H)-trione according to previous studies. Carbon dots were dissolved in seven solvents of water, methanol, ethanol, ethylene glycol, dimethylformamide, ethyl acetate and dichloromethane and found to have different luminescence properties including fluorescence intensity, emission peak position and fluorescence lifetime. Based on this principle, the carbon dots were used as fluorescent probes to detect the water content in the proton solvent ethanol and the non-proton solvent dimethylformamide. With the increase of water content, the fluorescence intensity of carbon dots in the ethanol-water mixture decreased, the emission peak position was red-shifted from 509 nm to 518 nm, and the fluorescence lifetime was shortened from 10.70 ns to 5.11 ns; the fluorescence intensity of carbon dots in the dimethylformamide-water mixture decreased, the emission peak position was red-shifted from 495 nm to 519 nm, and the fluorescence lifetime was shortened from 12.89 ns to 5.24 ns. The experimental results show that there is a linear response between the fluorescence intensity, emission peak position and fluorescence lifetime of carbon dots and the water content, and the detection range is as wide as 0~100%. It is speculated that these phenomena are caused by the change of polarity of the solution and the formation of hydrogen bonds between the carbon dots and the solvent. With the increase of water content in the organic solvent-water mixed solution, the hydrogen bond formed between carbon dots and water gradually replaces the hydrogen bond formed between carbon dots and organic solvent. In addition, since water has the highest polarity in the solvent, the polarity of the mixed solution increases with the increase of water content, and these affect the surface groups of the carbon dots leading to the solvation effect of carbon dots. In order to verify the universality of the method, the carbon dots were dissolved in methanol-water and ethylene glycol-water mixed solutions with gradient concentration of water content. The results showed that the fluorescence intensities, emission peak positions and fluorescence lifetimes of the carbon dots also responded linearly to the water content of the system, and the method was universally applicable. The linear response between fluorescence lifetime and water content is rarely seen in other studies related to the detection of water content in organic solutions, providing a new detection pathway for the determination of water content. The linear response between fluorescence intensity, emission peak position and fluorescence lifetime and water content all indicate that the carbon dots are potential probes to achieve rapid and sensitive detection of water content in organic solvents.