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.　Results　showed　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.　©,　2015,　Beijing　University　of　Technology.　All　right　reserved.