Abstract: In order to study the influence of external environmental conditions on cotton fiber quality in Liaohe basin, an experiment was conducted to compare the fiber quality of 2 cotton varieties‘( Liaomian 19’and‘AC- 33B’), 3 fruit setting periods (before hot season boll, hot season boll and autumn boll), 2 fruit setting positions (1- 4 and 5- 8 fruit branches). The fiber length, strength, micronaire, uniformity and elongation, and the variation coefficient of each index were compared and analyzed. The results showed that: the fiber quality of ‘Liaomian 19’and‘AC-33B’reached A or AA standard of short season cotton, the environmental conditions influenced micronaire more obviously. For different bolling stages and boll positions, the indexes and variation coefficients of fiber quality were different but had the similar rule, which was: the comprehensive cotton quality of mid and early bolls (before hot season boll and hot season boll) which formed in the mid and lower positions (1-4 fruit breaches) was better than that of the later bolls (autumn boll) which formed in the upper positions (5-8 fruit branches), indicating the impact of environmental conditions on cotton fiber quality. Overall, hot season boll has better fiber quality and should become the goal of high yield and quality cotton cultivation.