Abstract: 【Objective】 To study effects of different straw retting methods on the phosphorus balance of red soil fluecured tobacco farmland，to reveal the characteristics of phosphorus balance in the red soil flue-cured tobacco farmland ecosystem under straw retting，so as to provide a scientific basis for the prevention and control of non-point source pollution in small watersheds in central Yunnan.【Method】 Under natural rainfall conditions，different straw returning densities（0.75 and 1.50 kg/m²），different straw crushing particle sizes（1 and 5 cm），different straw heap retting processing（water，water and urea）were designed to study the effects of runoff and sediment phosphorus loss，soil phosphorus residue，flue-cured tobacco phosphorus absorption and phosphorus balance in the flue-cured tobacco slope farmland.【Result】 Given 1.50 kg/m² straw density，5 cm straw particle size，water retting compared with 0.75 kg/m² straw density，1 cm straw particle size，water and urea retting the runoff and sediment yield（0.22%-43.26%）could be effectively reduced.Given straw density of 0.75 kg/m²，straw particle size of 5 cm，and water retting，the phosphorus concentration loss （2.82%-66.67%，0.38%-57.53%）and phosphorus loss（the highest reduction was 63.89% and 64.74% respectively）in runoff and sediment could be effectively reduced.Effects of straw returning on soil total phosphorus（TP）residues in each soil layers were different，and the overall trend was increasing.After straw returning，the distribution of TP content was leaf>root>stem.The straw density of 1.50 kg/m²，straw particle size of 1 cm，water and urea retting could increase TP content in plant organs of flue-cured tobacco （0.60%-49.76%）and soil TP surplus （0.43%-13.97%）.【Conclusion】 Straw retting can improve and keep phosphorus in red soil flue-cured slope，reduce soil phosphorus loss and enhance soil phosphorus supply capacity，which is a significant measure to weaken agricultural non-point source pollution in the basin，comprehensively utilize straw resources，and promote the balanced development of agricultural ecology.