Photosynthetic　carbon　is　an　integral　part　of　carbon　cycle　in　plant-soil　system,　also　is　an　important　source　of　soil　organic　carbon.　In　this　study,　C-13　labeling　was　used　for　exploring　allocation　of　photosynthate-C-13　in　Phragmites　australis　-soil　system　undergoing　the　salt　marsh　restoration　project　by　freshwater　pumping　in　Yellow　River　Estuary　(YRE),　China.　Samples　were　collected　from　T-0　(before　labeling)　to　90　days　after　labeling　(T-4),　in　natural　salt　marsh,　5-,　10-　and　15-year　freshwater　pumping　areas,　respectively.　The　photosynthate-C-13　contents　of　soil　were　gradually　decreased　to　0　mg/g　at　T-4　in　most　areas,　while　it　was　2.21　mg/g　in　15-year　pumping　area,　higher　than　other　areas　at　the　last　sampling　time　(T-4).　And　the　allocation　of　photosynthate-C-13　in　soil　was　increased　from　3.58%　at　T-2　to　44.46%　at　T-3　in　natural　salt　marsh,　while　no　significant　change　was　found　in　other　areas　from　T-2　to　T-3,　followed　by　the　significantly　higher　photosynthate-C-13　proportion　in　soils　of　15-year　pumping　area　at　T-4.　EC　(R-2　=　0.5972)　and　small　macro-aggregates　proportion　of　soil　(R-2　=　0.4829)　had　positive　correlations　with　A　photosynthate-C-13　(the　value　of　photosynthate-C-13　in　underground　part　minus　that　in　soil);　silt　and　clay　fractions　proportion　of　soil　(R-2　=　0.7044)　had　negative　correlation　with　Delta　photosynthate-C-13.　Distribution　and　transportation　of　photosynthetic　carbon　in　the　underground　were　affected　by　soil　physical　and　chemical　properties.