Abstract: To illuminate the value of iaaM-transgenic upland cotton in cultivating Ⅰ type of high quality hybrid cotton, PCR was used for the molecular detection of four iaaM-transgenic upland cotton germplasms, two upland cotton germplasms with high fiber quality and four F1 hybrids. A block comparison test was conducted to analyze the economic characters. The results showed that four iaaM-transgenic male parents and their hybrid F1 appeared characteristic main band in 500 bp, but two female parents had no characteristic main band, which indicated that iaaM gene was dominant expression in hybrid F1 generation. The iaaM-transgenic upland cotton germplasms had higher lint percentage, bigger boll weight, more bolls per plant and lower abscission rate, but with smaller seed index and higher empty seed rate. The lint percentage, boll weight and boll number of hybrid F1 with iaaM gene were close with the iaaM-transgenic parents, which indicated that the three factors with iaaM-transgenic yield characters were dominant expression in hybrid F1. The fiber quality of two hybrid combinations reached Ⅰ type standard, and one combination still had positive competitive advantage in lint yield, compared with Ⅲ type contrast‘Suza201’. When iaaM germplasm is used as cross parent, if we choose the suitable cross matching, it is feasible in practice for breeding Ⅰ type of high quality hybrid cotton with yield competitive advantage.