The　magnetic　topological　insulator　EuSn2As2　is　known　to　crystallize　in　a　Bi2Te3-type　layered　structure　in　rhombohedral　symmetry　at　ambient　conditions　and　undergo　a　structural　phase　transition　toward　a　monoclinic　)5phase　under　increasing　pressure.　Here,　we　identify　by　ab　initio　calculations　a　new　high-pressure　rhombohedral　structure　(termed　the　gamma　phase)　in　R3　over　bar　m　symmetry　comprising　Sn-As-As-Sn　linear　chains　along　the　z　axis　via　the　formation　of　As-As　bonds　in　the　AsSn/SnAs　bilayers　with　strong　anisotropic　lattice　distortion　along　the　[001]　orientation.　This　pressure-densified　new　rhombohedral　phase　has　a　metallic　A-type　antiferromagnetic　ground　state　and　is　energetically　more　favorable　than　the　original　rhombohedral　structure　and　the　monoclinic　)5　phase　above　11　GPa.　Simulated　x-ray　diffraction　patterns　provide　an　excellent　match　to　the　previously　unexplained　distinct　diffraction　peak　around　14.7　degrees　found　in　experiments　for　EuSn2As2　above　13　GPa.　These　findings　offer　key　insights　into　a　new　type　of　high-pressure　phase　of　layered　magnetic　topological　insulators,　laying　a　foundation　for　further　exploration　of　this　intriguing　class　of　materials.