Polarization　photodetection　has　attracted　much　attention　as　a　promising　method　to　get　more　information　from　the　target　objects,　and　in　this　field,　two-dimensional　(2D)　materials　with　a　low-symmetric　structure　show　great　potential　for　their　ability　to　distinguish　light　with　different　polarization　direction.　However,　limited　by　the　intrinsic　crystal　structure　and　forbidden　bandwidth　of　such　materials,　there　are　hindrances　in　optimizing　polarization　photodetection　performance,　such　as　improving　the　anisotropic　current　ratio　as　well　as　expanding　the　detection　spectral　range.　Even　though　low-symmetric　materials　have　been　stacked　through　mechanical　transfer　as　a　possible　solution,　the　varying　relative　angles　between　different　materials　and　the　pollution　at　the　interface　induced　during　the　transfer　process　still　have　negative　effects　on　the　photodetection　performance　of　these　heterojunctions.　In　order　to　solve　the　mentioned　problems,　a　strategy　to　form　highly　low-symmetry　GeSe2-GeSe　heterojunctions　by　selenization　of　single　GeSe　crystals　has　been　proposed,　for　which　the　b-axis　direction　of　GeSe2　and　the　armchair　direction　of　GeSe　are　spontaneously　in　parallel.　The　synthesized　heterojunctions　with　type-II　energy　band　arrangement　can　reach　an　anisotropic　current　ratio　up　to　3.5　(at　808　nm)　and　exhibit　a　higher　absorption　compared　to　single　GeSe.　This　work　presents　a　scheme　for　preparing　low-symmetry　heterojunctions　by　in　situ　transformation,　which　suggests　a　potential　approach　for　optimizing　linearly　polarized　photodetectors　based　on　the　designed　heterojunctions＇　growth.