CdSe Quantum Dots have broad application prospects in many areas especially in biology due to the quantum effects. However, the CdSe QDs obtained by a traditional organic synthesis method are in soluble in water, which limits the application in biology. Also, the process of previous water system is more complicated and the time required is relatively long. Herein, we report a one-pot method to synthesize water-soluble CdSe QDs with excellent optical properties and structure. Importantly, the CdSe QDs exist in a mono-disperse state in water. We also examined the pH and temperature effect on the fluorescence intensity. This novel approach may improve the application of CdSe QDs used as a fluorescence probe in biology.