Method: The experiment selected the major local cotton varieties Biaoza A 1 and Xinluzao33 as test materials and designed different irrigation water quantity and nitrogen (N) fertilizer quantity. Objective: Dry matter accumulation and differences between varieties were analyzed. Result: Result indicated that the total dry matter accumulation showed the change pattern of "slow-fast-slow" in two cotton varieties during the whole growing stage. The total dry matter accumulation were increased with the increase of irrigation water quantity and nitrogen fertilizer quantity, the maximum increasing rates augmented, and fast rising periods were delayed. But over-irrigation would lead to decrease of the total dry matter accumulation. Conclusion: Biaoza A 1 was higher in dry matter accumulation than Xinluzao33 at different treatments; the difference was not significant between varieties between varieties in low irrigation, but significant in medium and high irrigation.
