<p>In this study, a simulation of the structural phase transition mechanism of SnO₂ (Cassiterite), selected among the rutile-type stable metal dioxides, has been carried out. Calculations were performed in the frame of density functional theory (DFT). Using the ab-initio technique, the structural phase transition behaviors and intermediate phases of SnO₂ under high pressure were investigated with the Siesta code. Generalized gradient approximation (GGA) was selected to find the exchange–correlation energy. Initially, the rutile-type SnO₂ structure was optimized at zero pressure, and then the pressure was increased up to 170 GPa with an increment of 10 GPa. The initial rutile-type structure of SnO₂ with space group P4₂/mnm (No. 136) transformed into the cotunnite type structure with space group Pnma (No. 62) at 100 GPa. During the phase transformation of SnO₂ from rutile type to cotunnite type at 100 GPa pressure, intermediate phases Pnnm (Orthorhombic) → P2₁ (Monoclinic) → P₁ (Triclinic) → Pc (Monoclinic) → P2₁/c (Monoclinic) were determined for the first time in this study. Energy and enthalpy calculations were performed to investigate the compatibility of the determined stable phase transition with the experimental results. For the electronic properties, the band structures and density of states are calculated and analyzed in detail. The findings obtained from the calculations are in accordance with the literature.</p>