Hydrolytic enzyme activities and environmental factors play important roles in litter decomposition. To better understand the changes in carbon (C), nitrogen (N), and phosphorus (P) dynamics and hydrolytic enzyme activities during litter decomposition of Kandelia obovata, the difference in decomposition between K. obovata population (local field) and Spartina alterniflora Loisel. population (away field) was measured; K. obovata population aged 20 years located in Culu Island of the Min River estuary was used. The results of the litter bag test revealed the following. 1) The accumulative mass loss rate in the local field was significantly higher than that in the away field throughout decomposition (P < 0.05), whereas the accumulative mass loss rate and decomposition rate exhibited significant difference with decomposition time (P < 0.01). In contrast, the total carbon content (TC), total nitrogen content (TN), total phosphorus content (TP), and stoichiometry were comparable between the local field and away filed (P > 0.05), but exhibited significant difference with decomposition time (P < 0.01). 2) The accumulative mass loss rate negatively correlated with the TC content, carbon/nitrogen ratio (C/N), and acid phosphatase (AP) activity (P < 0.01), whereas they exhibited a significant positive correlation with the TN content (P < 0.01). The decomposition rate positively correlated with the TP content (P < 0.01). 3) The activity of AP correlated with the TC, TN, and TP content, C/N ratio, and carbon/phosphorus ratio, whereas it positively correlated with soil temperature (P < 0.01). The activity of β-1,4-glucosidase and β-1,4-N-acetylglucosaminidase showed a significant positive correlation with the nitrogen/phosphorus ratio (P < 0.01), whereas they negatively correlated with soil electrical conductivity (P < 0.05). Cellobiohydrolase activity positively correlated with the TC content. The foliar litter decomposition of K. obovata correlated with the activity of some hydrolases and the content of nutrients. It was also significantly affected by soil environmental factors. The activity of hydrolase was affected by substrate concentration and soil environmental factors during litter decomposition.