Abstract: This paper aims at exploring the tolerable water depth and duration of submergence for early rice during the heading and flowering stages in the Poyang Lake Basin. To this end, four main early rice varieties planted in the basin are selected for submergence tolerance tests during their heading and flowering stages, and the findings are summarized as follows. The plant height of each treatment increases or is compared with that of control group after flooding stress. Submergence stress during the heading and flowering stages are linked to rice yield reduction, whereas submergence depth and duration are correlated with effective panicle number, seed setting rate and 1 000-grain weight.Moreover, different varieties also present different submergence tolerance, e.g., Taiyou 398 and Xiangzaoxian 45 are considerably adaptable to submergence stress. Taking rice yield reduction ≤10% as the acceptable standard, the tolerable water depth of submergence for Zhuliangyou 171 and Zhongjiazao 17 during their heading and flowering stages is 1/2 of their plant height, while the tolerable duration of submergence is 1～3 days. Contrary to the above, the tolerable water depth of submergence for Xiangzaoxian 45 is 2/3 of its plant height, while the tolerable duration is 1～3 days. Moreover, Taiyou 398 demonstrates impressive submergence tolerance, boasting a tolerable water depth of 2/3 of its plant height and a 3～6 days tolerable duration.