A model is established for a microcavity laser with cadmium selenium/cadmium sulfide (CdSe/CdS) core/shell quantum dots (QDs) as a lasing medium, The research was organised to develop and solve the rate equations for the above mentioned microcavity laser to calculate the output parameters during lasing. Using time-resolved fluorescence spectroscopy, the radiative life time of the lasing medium was measured along with its fluorescence and absorption spectra. A model is also established on the basis of the segment contact method (SCM) to demonstrate the threshold gain profile using the absorption spectrum of CdSe/CdS core/shell type II QDs residing in the cavity. A laser cavity of size 1 mu m was pumped with an optical source (532 nm) to achieve an optimised laser peak at 470nm,