Abstract: 【Objective】 To understand the morphological changes of fiber development in different upland cotton varieties, and compare the morphological differences in important stages of fiber development. 【Methods】 Xinluzhong 82, Xinluzhong 70, Xinluzhong 38 and 15-1242 were taken as materials to observe the ovules of the fibers from the day before flowering to the day after flowering, the fibers of 21 days and 28 days of development, and mature fiber. 【Results】 It can be seen from the observation of ovules that, with the increase of flowering time, the number of protuberances or elongation of ovules epidermal cells gradually increases, and the number of protuberances on the day of flowering is 5,900-7,800 per square millimeter, and the number of protuberances in the middle boll is the largest, which is more than 7,000 per square millimeter. The number of elongation in the day after flowering ranged from 3,000 to 6,400 per square millimeter, with the largest number of elongation in the middle boll, above 5,000 per square millimeter; the 21-day and 28-day fibers show a short growth period Varieties with a longer growth period enter the fiber thickening period earlier, and the shorter the growth period, the greater the degree of fiber distortion during the same development period. The speed of entering the thickening period in different flowering periods is shown by the fibers that bloom on July 14. The fiber that blooms on July 21 is the earliest, and the fiber that blooms on July 21 is the latest; the twist and longitudinal lines of the middle section of the mature fiber are different in different blooming periods. The twist and depth of Xinluzhong 70 are the most obvious, and Xinluzhong 38 is the most obvious. Not obvious. 【Conclusion】 Based on the fiber development stage of different varieties, the fiber development process of the short growth period is faster.The fiber development process of the different flowering period is that the fiber development of the middle boll is faster than the lower and upper parts.In view of the distortion and depth of mature fibers, the differences in fiber morphology of different varieties and flowering stage may be one of the reasons for the differences in fiber quality.