[Objective] To analyze the influence mechanism of water and salt contents on soil nutrient and enzymatic activity, in order to provide scientific basis for exploring the effect of seawater intrusion on coastal wetland soil. [Methods] The surface soil of the coastal wetland in Jiaozhou Bay was collected and the simulation experiments were conducted in laboratory to determine the soil nutrient index and enzymatic activity under different water salt gradients. [Results] Soil pH value and bulk density (BD) were significantly affected by salinity and moisture, respectively. With the increase of soil water gradient, the total organic matter (TOM), ammonium nitrogen (NH₄⁺-N), available phosphorus (AP), available potassium (AK), sucrase activity (SA), urease activity (UA) and alkaline phosphatase activity (APA) increased initially and then decreased, reaching the maximum value at 30% water gradient. TOM, AP, AK, SA, UA and APA decreased with the increase of soil salinity gradient, while NH₄⁺-N showed an opposite variation trend. The correlation analysis showed that SA was positively correlated with TOM, AP and AK, and APA was positively correlated with TOM, AP, AK and BD. In addition, UA was positively correlated with soil pH value and BD, and had a certain correlation with NH₄⁺-N. [Conclusion] In a certain range, excessive or low water content and increased salt content can inhibit the soil nutrient contents and enzymatic activities, and there is a close relationship between soil nutrients and enzyme activities.