In this work, fluorescent nitrogen-doped carbon dots (N-CDs) were pyrolysis synthesized using edetic acid and acrylamide as precursors without further surface modication. The as-prepared N-CDs were mono-dispersed spherical nanoparticles with an average diameter of 3.25 nm. The blue fluorescence emission was dependent of the excitation wavelengths, releasing stable and strong blue fluorescence under the maximum excitation wavelength. More strikingly, after adding picric acid (PA), the fluorescence of N-CDs aqueous solution gave rise to the obviously fluorescence quenching due to the inner filter effect. Under the optimum conditions, the fluorescence probe can be used for the selective detection of PA with a wide linear relationship in the range of 0.01–32 μM and the detection as low as 0.046 μM. Depending on the fluorescence quenching phenomenon, the resultant fluorescent probe for accurate and selective monitor of PA in Fenhe river samples was explored. The recoveries fell in the range of 97.13%–106.21% and the relative standard deviation was below 3% with satisfactory results.