Abstract: 【Objective】 The purpose of this study is to provide theoretical foundation for the selection of superior parents, hybrid combinations and F₂ of cotton product application. 【Method】 Eight parents from areas of Yellow River, Yangtze River and Northwest Inland were divided into two groups of 5 or 3 respectively, and made crosses according to NCⅡ design of the incomplete diallel cross (5×3); The plant height, leaf seedling SPAD values, and photosynthesis parameters of the parental, F₁, F₂ and control varieties were determined under field environmental conditions. 【Result】 The results showed that, both broad sense heritability and narrow sense hetriability in plant height, SPAD, photosynthetic parameter were relatively high and some traits of F₂ heritability was higher than that of F₁ in seeding stage. Every trait of the parent with best general combining ability(GCA) were P₁(Zhong 901), P₂(ZB), P₆(DT) and P₇(Z98) in seeding stage. The hybrid F₁ and F₂ which showed better special combining ability in each character at seedling stage were combination 2(Zhong901×Z98), combination 5(ZB×Z98) and combination 7(SJ48×DT). The 15 hybrid combinations F₁ and F₂ showed different competitive advantages in seeding stage compared with the contol, and some combinations showed significant differences. Mostly combinations of F₁ and F₂ showed positive heterosis advantage with competitive advantage, the mid-parent and high-parent in plant height, SPAD value, net photosynthetic rate and stomatal conductance, but in others traits, F₁ and F₂ combinations showed negative heterosis advantage with mid-parent and high-parent. 【Conclusion】 In this study, based on breeding practice of hybrid cotton varieties, the heterosis performance and combining ability in different generations of traits at seedling stage are systematically analyzed. It is found that the hybrid combination composed of the male parent P₇ (Z98) group performs better than other combinations in the seedling stage traits and has a greater utilization potential.