Abstract: Carbon quantum dots (CQDs) are a new fluorescent material with stable fluorescence, low toxicity and many other superior properties that make their applications in biology possible. CQDs in wood charcoal were created by a 5N HNO₃ solution using three different methods, reflux, microwave and ultrasound methods. Factors that determine the fluorescence quantum yield were examined and preparation conditions were optimized. Results indicated that the fluorescence quantum yield of CQDs prepared by the reflux method was highest among the three methods. The CQDs prepared by this method were modified by poly(ethylene glycol)2000 to increase the fluorescent lifetime and the quantum yield. The reaction of the modified CQDs with bovine serum albumin was investigated by ultraviolet absorption spectrometry and fluorescence spectrometry, which revealed a static quenching behavior.