At　present,　the　application　scenarios　based　on　BIM+GIS　technology　are　widely　used　in　various　infrastructure　industries.　However,　in　the　process　of　2D　to　3D　transformation,　the　application　scenarios　of　multi-source　heterogeneous　data　fusion　in　the　reconstruction　and　expansion　projects　of　long　lines　and　highways　have　not　yet　been　studied.　This　paper　focuses　on　the　reconstruction　and　expansion　project　of　long-line　expressway,　classifies　the　data　according　to　the　characteristics　of　the　project,　establishes　the　model　coding　suitable　for　the　whole　life　cycle,　and　proposes　a　model　coding　processing　method　based　on　json　mapping　form,　which　improves　the　maintenance　of　the　model　and　coding.　This　paper　proposes　a　set　of　data　lightening　methods　for　the　whole　process,　aiming　at　data　lightening　for　terrain　and　structural　models　with　large　volumes,　and　realizing　the　load　lightening　capability　after　large　volumes　of　data　enter　the　platform.　At　the　same　time,　in　order　to　ensure　the　consistency　of　model　information　data　content　and　spatial　location　accuracy,　a　set　of　BIM　and　GIS　data　coupling　verification　method　and　a　positioning　method　of　coordinate　system　transformation　between　new　and　old　structures　are　established.　Finally,　the　application　value　of　multi-source　heterogeneous　data　fusion　is　verified　through　the　reconstruction　and　expansion　project　data　of　a　long　expressway.　The　results　show　that　the　whole　life　cycle　encoding　mode　using　json　mapping　form　improves　the　usability　of　the　model　and　encoding.　The　lightweight　processing　of　large　data　improves　the　loading　capability　of　data.