Abstract:Eight combinations were obtained by crossing Sumian 12, Zhongmian12, Sumian 16 and J011, respectively, with mutual father parents Xinyoumian 68 and K-79, two cotton lines with high fiber quality and yield and multi-resistances, in 2004, a screening method, based on principal component analysis of average boll numbers and retention per plant during peak flowering and boll-setting periods in the field, maximum pollen germination and pollen tube length in an in vitro culture experiment for cotton hybrid combinations, was used in the present study in 2005 and 2006 and, as a result, the hybrids could be classified as tolerant(+PC1 and +PC2), moderately tolerant(+PC1 and-PC2), moderately susceptible(-PC1 and +PC2) and susceptible (-PC1 and-PC2)to high temperature stress according to the scores of the first two principal components vectors. The high-temperature tolerant hybrid JL06 screened from the 8 combinations performed with strong boll setting, wide adaptability and high yield during two-year more and multi-site experiments, and approved by Hunan Crop Variety Approval Committee in 2009. A new cultivar for high temperature tolerance can be developed by the method during cotton breeding program to stabilize yields for consistently high yields in the present cotton-producing environment and in the future warmer climate.