Enhanced blue fluorescent carbon nitride quantum dots (g-C3N4QDs) were synthesized by a simple solvothermal "tailoring" process from bulk g-C3N4 and analyzed by various characterization methods. The as-obtained g-C3N4QDs were successfully applied in the determination of tetracycline (TC) with a good linear relationship in the range of 0.23-202.70 μM. The proposed fluorescent sensor shows excellent stability, good repeatability, high selectivity and outstanding sensitivity to TC with a low detection limit of 0.19 μM. The fluorescence quenching mechanism of g-C3N4QDs with TC was mainly governed by static quenching and the inner filter effect. The method was successfully applied to monitor TC in tap water and milk powder samples.