CdSe quantum dots (QDs) with a uniform size distribution were synthesized using a droplet-based microfluidic reactor. The droplet-based microfluidic reactor enabled continuous production of CdSe QDs at a temperature of less than 250 °C in an extremely shorter reaction time (less than 30 s) when compared with the batch reactor. The photoluminescence (PL) and ultraviolet (UV) absorption spectra of the CdSe QDs were recorded at different reaction times and the size and optical properties of the QDs were discussed. The structure morphology and elemental composition of the CdSe QDs were determined using a transmission electron microscopy (TEM) and electrondispersive spectroscopy (EDS). The size of CdSe QDs prepared using the microfluidic reactor was estimated to be from 1.6 to 2.6 nm with an average size of 2.2 nm. This droplet-based microfluidic reactor has the potential to be automated system continuous synthesis of CdSe QDs.