This study explores the impact of quantum dot (QD) height and material concentration on the density of states (DOS) and absorption coefficient of CdSe/ZnSe QD. A multi-band envelope (k·p) approximation computes energy levels and wave functions, incorporating strain effects via deformation potentials. A reduction in QD height from 7 nm to 6 nm results in a blue shift of approximately 7.3 meV in the absorption spectrum and an increase in absorption values by 30 × 103 cm−1, attributable to the quantum confinement effect. Additionally, increasing strain values from 0.72 to 2.12% significantly enhances the absorption coefficient by 9 × 104 cm−1 and induces a shift towards higher energy in the peak. This work highlights the critical role of QD geometry and strain engineering in fine-tuning the optical properties of QDs, offering valuable insights for optimizing QDs in next-generation optoelectronic devices.