Abstract: This paper optimized the structure of the metastable face centered cubic Ge₂Sb₂Te₅ using the software CASTEP based on the density functional theory method. The numerical models were established by the local density function LDA CA-PZ and the generalized gradient approximation GGA PBE,and the effects of the two methods on the band,density of states,partial density of states,electron density,and other related properties were further compared and analyzed. The properties of the structure were obtained.Resultsshowed that the structure of Ge₂Sb₂Te₅ calculated by LDA CA-PZ had lower energy and better stability than that simulated by using GGA PBE. However,the lattice constant calculated by GGA PBE agreed well with experimental results while it was narrowing calculated by LDA CA-PZ. The metastable Ge₂Sb₂Te₅ presented the typical metallic properties with no band gap while the greatest impact on the material properties was Te atoms.