Straw　addition　can　increase　the　content　of　soil　organic　carbon　(SOC),　and　affect　the　content　of　aggregates　and　organic　carbon　fractions.　The　changes　in　aggregates　and　organic　carbon　fractions　in　the　natural　salt　marsh,　10-year　and　15-year　freshwater　pumping　areas　in　the　Yellow　River　Estuary　were　studied　by　120-day　field　in　situ　culture　experiments　with　Phragmites　australis　straw　addition.　The　results　showed　that　straw　addition　mainly　enhanced　the　soil　aggregate　stability　in　the　10-year　freshwater　pumping　area,　and　the　organic　carbon　content　of　small　macro-aggregates　increased　significantly　by　26.36%　(P　＜　0.05).　In　particular,　the　content　of　coarse　particulate　organic　carbon　(cPOC)　with　small　macro-aggregates　in　all　areas　increased　significantly　with　the　addition　of　straw　(P　＜　0.05).　For　small　macro-aggregates　in　the　10-year　pumping　area,　the　cPOC　contents　increased　significantly　by　21.73　g/kg　(P　＜　0.05);　and　were　significantly　higher　than　the　fine　particulate　organic　carbon　(fPOC)　and　mineral-associated　organic　carbon　(mSOC)　contents,　as　the　fPOC　contents　in　micro-aggregates　increased　by　85.92%　(P　＜　0.05).　Additionally,　the　cPOC　contents　of　small　macro-aggregates　and　fPOC　contents　of　micro　aggregates　increased　by　34.59%　and　43.24%　in　the　15-year　pumping　area.　The　contents　of　mSOC　were　the　lowest　in　different　aggregates　across　all　areas.　Thus,　straw　addition　had　a　significant　effect　on　the　contents　of　cPOC　and　fPOC,　while　freshwater　pumping　in　the　YRE　could　affect　the　distribution　of　fPOC　and　mSOC　with　aggregates.　(c)　2021　Elsevier　B.V.　All　rights　reserved.