With radical global climate change and global warming, high temperature stress has become one of majorfactors exerting a major influence on crop production. In the cotton (Gossypium hirsutum L.)-growing areasof China, especially in the Yangtze River valley, unexpected periodic episodes of extreme heat stressusually occur in July and August, the peak time of cotton flowering and boll loading, resulting in lower bollset and lint yield. Breeding programs for screening high temperature-tolerant cotton germplasm and cultivarsare urgent in order to stabilize yield in the current and future warmer weather conditions. In thepresent study, 14 cotton cultivars were quantified for in vitro pollen germination and pollen tube growth inresponse to temperatures ranging from 10 to 50℃ at 5℃ intervals. Different cotton genotypes varied intheir in vitro pollen germination and pollen tube length responses to the different temperatures. Maximumpollen germination and pollen tube length ranged from 25.2% to 56.2% and from 414 to 682μm, respectively.The average cardinal temperatures (Tmin, Topt, and Tmax) also varied among the 14 cultivars and were 11.8,27.3, and 42.7℃ for pollen germination and 11.8, 27.8, and 44.1℃ for maximum pollen tube length. Variationsin boll retention and boll numbers per plant in field experiments were found for the 14 cotton cultivars andthe boll retention and boll retained per plant on 20 August varied considerably in different years accordingto weather conditions. Boll retention on 20 August was highly correlated with maximum pollen germination(R2=0.84) and pollen tube length (R2=0.64). A screening method based on principle component analysis ofthe combination of pollen characteristics in an in vitro experiment and boll retention testing in the fieldenvironment was used in the present study and, as a result, the 14 cotton cultivars could be classified astolerant, moderately tolerant, moderately susceptible and susceptible to high temperature.