We apply 8-band k.p model to study InAs/GaAs quantum dots (QDs). The strain was calculated using the valence force field (VFF) model which includes the four nearest-neighbour interactions. For the optical properties, we take into account both homogeneous and non-homogeneous broadening for the optical spectrum. Our simulation result is in good agreement with the experimental micro-photoluminescence (mu-PL) result which is from InAs/GaAs QD vertical cavity surface emitting lasers (VCSELs) structure wafer at room temperature. Accordingly, our simulation model is used to predict the QD emission from this QD-VCSELs structure wafer at different temperature ranging from 200-400 K. The simulation results show a decrease of 41 me V of QD ground state (GS) transition energy from 250-350 K. The changes of QD GS transition energy with different temperature indicate the possible detuning range for 1.3-mu m wave band QD-VCSELs applications without temperature control. Furthermore, QD differential gain at 300 K is computed based on this model, which will be useful for predicting the intrinsic modulation characteristics of QD-VCSELs.