Spartina alterniflora is a typical invasive species in Jiaozhou Bay coastal wetland. The effects of Spartina alterniflora invasion on soil total iron content variations in estuary wetland of Jiaozhou Bay were studied. Soil samples were collected from Spartina alterniflora wetland and mudflat in March, May, July, September, and November 2017. The contents of total iron, organic matter, soluble salt, pH, water content, bulk density, and particle size in soil were measured and analyzed. The results showed that Spartina alterniflora invasion significantly increased total iron contents in soil, and the differences were significant (P < 0.05) in the 0-50 cm soil layers of the two sampling regions. The total iron contents of Spartina alterniflora wetland increased first and then decreased in the vertical direction in May and July. Compared with the mudflat in the same sampling month, the total iron contents of Spartina alterniflora wetland increased by 25.36%, 29.50%, 17.52%, 30.28%, and 14.48%, respectively. The correlation analysis showed that the total iron contents in the soil of Spartina alterniflora wetland and mudflat were positively correlated with the contents of organic matter and soluble salt (P < 0.01). The total iron content in mudflat was positively correlated with water content (P < 0.01), and negatively correlated with bulk density (P < 0.01), which indicated the total iron contents in the two sampling regions were greatly affected by organic matter and soluble salt.