In order to clarify the effects of crab activities on the changes of available nutrients in wetland soils, soil DOC, MBC, NH₄⁺-N, NO₃^--N, Fe and their valence contents under the interference of crabs from different tidal flats in Minjiang River estuarine wetlands were measured. The results showed that the average contents of DOC and MBC in soil were 95.98 and 11.13 mg/kg, respectively in the crab group and 106.99 and 7.54 mg/kg in the control group, respectively (P<0.05). The content of MBC in soil of crab group was higher than that of control group (P<0.05). The highest and lowest values of the two contents appeared in summer and winter respectively, and were significantly higher in summer than in other seasons (P <0.05). The average values of soil NH₄⁺-N and soil NO₃^--N in the crab group were 22.45 and 1.08 mg/kg, respectively, and those in the control group were 23.65 and 1.44 mg/kg. The content of NH₄⁺-N in soil of crab group was lower than that of control group (P<0.05), while the content of NO₃^--N in soil of crab group was lower than that of control group (P<0.05). The contents of NH₄⁺-N and NO₃^--N in soil were significantly different in different seasons (P<0.01). The soil total iron content in crab group was slightly higher than that in control group (P>0.05). The content of Fe²⁺ in soil of crab group was significantly higher than that in control group (P<0.05). There was no significant difference in soil Fe³⁺ content between crab group and control group (P>0.05). In different seasons, soil total Fe, Fe²⁺ and Fe³⁺ contents were significantly different (P<0.01).