Abstract: 【Objective】Through analysis of stoichiometry and hydrology, the right growing environment of the main species of Bruguiera sexangula var. rhynochopetala and Avicennia marina seedlings and their conservation and restoration in China could be figured out.【Method】The influences of waterlogging time on stoichiometric characteristics of Bruguiera sexangula var. rhynochopetala and Avicennia marina seedlings in different organs (leaf, stem and root, respectively) were studied using the automatic tidal-simulation device in sand culture of greenhouse. The contents of 8 macroelements and 5 microelements were determined in the waterlogging treatments, respectively. 【Result and conclusion】The content of K, P, Na, Cl, Mg, Ca, Al, Fe, Mn, B differed significantly in seedlings when waterlogging stress varied. The result of the experiment showed waterlogging had a significant effect on the distribution characteristics of elements in different organs of seedlings, and different species differed in stoichiometric characteristics. The elemental content in leaf was more obvious in waterlogging than that in stem and root of B. sexangula var. rhynochopetala and A. marina seedlings. The result of waterlogging treatment showed the contents of Fe, Al, Mn, Ni, B increased in leaf continually, decreasing in root slightly. The Fe and Al content in 20 h waterlogging about 4.2 and 6.6 times higher than that of 2 h in B. sexangula var. rhynochopetala seedlings. The Fe, Al, Mn, Ni, B in 24 h waterlogging about 4.7, 1.1, 3.5, 4.0 and 1.5 times than that of 2 h in A. marina seedlings. This is possibly one of the most important features of mangrove species in stoichiometry. There is a significant correlation between the change in Mg and Ca in different organs of two species and waterlogging levels.