Abstract: 【Objective】Understand the heterosis of island-upland hybrid cotton and island-island hybrid cotton,in order to provide theoretical basis for the breeding of mechanical harvesting hybrid long-staple cotton varieties.【Methods】The long fruit branch,zero fruit branch island cotton and early-maturing,high-yield and insect-resistant long fruit branch upland cotton varieties（lines）were used as parents,hybrid cotton combinations of island-upland hybrid cotton and island-island hybrid cotton were made. The plant characters,boll traits and fiber quality of parents and hybrid cotton were compared.【Results】Island-island hybrid cottons had compact plant-type,small bolls,low lint percentage,low sterile seeds rate,and superior fiber quality. The three island-island hybrid cotton had an average fibre length of 36.0 mm,fibre strength of 45.9 cN/tex and micronaire value of 3.5. The island-upland hybrid cotton had loose tower plant-type,big bolls,high lint percentage,and high sterile seeds rate. Among them,the fiber quality of WT114×Xinhai No. 51 and WT117×Xinhai No. 63 met the quality standards of long-staple cotton.【Conclusion】Island-island cotton hybridization could breed super long-staple cotton varieties（lines）. With proper hybridization,the fiber quality of island-upland hybrid cotton varieties（lines）could reach the long-staple cotton standard as well. Island-upland hybrid cotton was suitable for large area mechanical harvesting.

Key words: Island cotton, Upland cotton, Heterosis, Plant characters, Quality traits