Abstract: In order to study the antagonism of plant growth hormones to the ethylene induced abscission of cotton boll. The results of a series of experiments are summarized briefly as follows: First of all, we found that ethylene had abscission-promoting effect on cotton boll. The percentage of abscission of cotton boll induced by ethrel was 100%. The abscission-promoting effect of ethylene on the cotton boll was inhibited not only by gibberellin but also by zeatin. At the end of the experiment it was found that the ovaries which were treated with ethrel in the presence of gibberellin or zeatin can continue to grow and develop into parthenoearpie fruits. In addition, the growth and development of the cotton boils, especially seeds and fibres, were significantly affected by ethylene in the presence of gibberellin.