With anhydrous citric acid and o-phenylenediamine as carbon sources, solvent-dependent emitting carbon nanodots are prepared by the one-step solvothermal method. The morphology and structure of the prepared carbon dots are characterized using atomic force microscope. It is found that the carbon quantum dots have a uniform height around 1.5 nm, and are mainly consist of few layers of graphene. The optical features of as-prepared carbon quantum dots are further confirmed by photoluminescence (PL) spectra and UV-visible (UV-Vis) absorption spectroscopy. It is found that the main absorbance is attributed to the carbon core and the surface states, and the maximum absorption occurs at wavelengths of 285 nm and 430 nm. In addition, the fluorescent emission in organic solvents peaks at 515 nm and its corresponding emission wavelength is the luminescence wavelength of surface defect state. With the increase of water content in the system, the emission peak red-shifts and the maximum emission intensity gradually decreases. When the water content (volume fraction) is in the range from 10% to 100%, the fluorescence signal intensity is linearly proportional to water content, and the detection limit of water content is 0.1% under the optimal condition. The experimental results confirm that these novel carbon quantum dots have a potential application as a probe and a sensor for the real-time quantitative detection of water content in various organic solvents. The results obtained here not only broaden the application range of carbon nanodots, but also provide a simple and effective method to detect water content in organic solvents.