[en] Highlights: • Glycine–modified Carbon dots (G-CDs) with high fluorescent quantum yield (QY = 31%) were prepared by microwave-assisted method. • G-CDs were stability at biological system, and had low cytotoxicity. • Human transferrin (hTf) had one type of binding site with G-CDs, and the fluorescence quenching mode was static quenching process. - Abstract: Luminescent carbon dots (CDs) are new fluorescent materials and widely used in biomedical fields. In this paper, CDs were prepared using citric acid and glycine (denoted G-CDs) by one-step microwave-assisted method and characterized by transmission electron microscopy (TEM), power X-ray diffraction (XRD), nuclear magnetic resonance (¹³CNMR), and Fourier transform infrared (FT-IR). The results showed that glycine was better than PEG200 or hexadecyltrimethyl ammonium bromide (CTAB) as the modification in reaction. The prepared G-CDs had the sizes about 10 nm, high fluorescent quantum yield (QY) up to 31%, and stability at biological system. Moreover, G-CDs had low cytotoxicity. Our results verified that amino group (or secondary amines) had a significant effect on the QY; one-step microwave-assisted method was simple, efficient and green. The further experiments about the interaction of G-CDs with human transferrin (hTf) were also detected. Data showed that there was a strong interaction between G-CDs and hTf, and one type of binding site between them. The quenching mode of fluorescence of hTf with G-CDs was static quenching process.