In recent years, more and more researchers pay attention to the synthesis of water-soluble fluorescent carbon dots. Compared with the traditional cadmium-based, silicon-based quantum dots and organic dyes, carbon dots with low toxicity and high stability can be chemically modified and be compatible with a variety of organic, inorganic, and biological molecules, and can be applied in many areas. The fluorescence carbon dots were prepared by one step microwave method using ascorbic acid as raw materials. The carbon dots were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), ultraviolet-visible spectrophotometry, fluorescence spectrophotometry, and Fourier transform infrared spectrophotometry(FTIR). The results showed that the carbon dots have approximate spherical morphology, uniform size, good dispersion and non-agglomeration, good fluorescence properties. The carbon dots were rich in carboxyl and hydroxyl groups and had highly hydrophilic nature. The emission wavelength of carbon dots depended on the excitation wavelength. Furthermore, these carbon dots also had good fluorescence properties in a wide pH range.