We　report　the　sublimation　and　phase　transformation　mechanisms　of　a　two-dimensional　(2D)　chalcogenide　SnSb2Te4　using　a　lab-developed　in-situ　electro-thermal　testing　system　on　a　Cs-corrected　transmission　electron　microscope.　It　reveals　that　the　sublimation　process　is　primarily　governed　by　the　surface　energy　mechanism,　following　an　anisotropic　route.　The　van　der　Waals　(vdW)　layers　ending　with　Te　atoms　lead　to　the　preferential　sublimation　on　(003)　plane,　with　the　(1　1　4)　and　(117)　planes　accommodating　the　sublimation.　It　is　uncovered　for　the　first　time,　that　the　preferential　and　accommodated　sublimation　of　Te　and　Sb　atoms　along　the　vdW　planes　results　in　short-range　diffusion　inducing　a　phase　transition　from　rhombohedral　SnSb2Te4　to　rock-salt　(Sn1-xSbx)　Te.　These　results　highlight　complex　physics　processes　of　2D　materials　under　service　conditions　and　the　route　of　atomic-resolved　electro-thermal　research　platforms　for　investigations　of　complex　atomistic　mechanisms　of　2D　materials　by　thermal-electric　external　fields.