This study aimed to determine the effect of waterlogging on the contents of C、N、tannins and Chlorophyll in the leaves of Kandelia candel (L.) seedlings, which were planted at various topographic sites in an intertidal zone of Tongan Bay, Xiamen, China. The experimental plots were on a slop and showed a maximal elevation difference of 1.6 m. Three experimental plots were set up in bare areas of intertidal zones. The mean elevations of the plots were 0.4 m, 1.0 m and 1.6 m respectively. The intertidal elevation affects tidal inundation and the inundation period. At 1.6 m above the zero tidal level of Huang Ocean, Kandelia candel seedlings showed best growth and the higest tannin concentrations and C/N ratios. Tannin concentrations and C/N ratios tended to decline with decreasing elevation. The results showed that changes in the C、N and tannin concentrations in response to waterlogging. This indicates that longer waterlogging time resulted in lower C/N ratios. The responses of tannins to the altered C/N ratios were that lower C/N ratios resulted in lower tannin concentrations of leaves, decreased by 44.6% and 70.5%, respectively, the biomass of Kandelia candel seedlings decreased by 18.2% and 47.0%. In fact, there was a significant positive correlation between tannin concentrations and C/N ratio (R=0.8425). The response of C、N and tannins in leaves to waterlogging was consistent with carbon-nutrient balance hypothesis.