Due to the wide range of tunable emission peaks, CdSe quantum dots (QDs) and CdSe/ZnS core-shell QDs have attracted many attentions from researchers. Refluxing method was adopted to synthesize CdSe QDs and CdSe/ZnS core-shell QDs, and transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis absorption spectroscopy (UV-Vis) and photoluminescence spectra (PL) were used for characterization in this paper. The TEM images show that the size distribution of QDs is wide and the crystallinity is high. From the XRD spectra, it can be found that CdSe QDs possess zinc-blende structure, and the peak shifts to higher angle when ZnS shells are grown along the crystal plane by epitaxial growth method. From the UV-Vis and PL spectra of CdSe QDs, an absorption peak and a defect emission peak with large half width can be detected at 500 nm and 644 nm, respectively. With the refluxing time increasing, an intrinsic emission peak occurred at 577 nm. The ZnS outer layer can not only increase the luminescence intensity of CdSe QDs, but also further improve the stability. This synthesis method saves energy, possesses high production efficiency, friendly environmental protection, which has a larger application area.