Cadmium pollution is very common in mangrove ecosystem in China, and the pollution situation is serious. Zinc has been used to reduce cadmium accumulation in soil and plants, and phenolic acid metabolism plays an important role in plant response to stress. Therefore, the aim of this study was to clarify whether zinc alleviates cadmium toxicity in mangrove plants through phenolic acid metabolism. The cadmium contaminated Kandelia obovata was treated with different concentrations of (80,300,400mg/kg) ZnSO4 in pot experiment. The results showed that the cadmium content and zinc content of Kandelia obovata in its leaves were in the range of 0.077 ~ 0.197mg kg− 1 dw and 90.260 ~ 114.447 mg kg− 1 dw under different zinc treatment concentrations. The synthesis of phenolic acid metabolites such as 4-hydroxy benzoic acid, chlorogenic acid and cinnamic acid increased. Low dose zinc sulfate treatment had significant positive effects on the biomass, phenolic acid metabolization-related enzyme activities, antioxidant capacity, chlorophyll and soluble sugar contents of cadmium-contaminated mangrove plants. The results showed that low dose of Zn could enhance the metabolism of phenolic acid and synthesize more phenolic compounds such as hydroxycinnamic acid and hydroxybenzoic acid to increase the antioxidant capacity of mangrove plants.