Objective:To study the differential expression and correlation of salivary secretory immunoglobulin A (sIgA) and peripheral blood hemoglobin (Hb) levels in children with different severity of dental caries.Methods:This study was a case-control study, selecting 106 children with dental caries who received treatment at Jiaxing Maternal and Child Health Hospital from December 2020 to June 2022 as the observation group, and 100 healthy children without dental caries during the same period as the control group. We compared the salivary sIgA and peripheral blood Hb levels between two groups of children. Children with dental caries were divided into mild group (2-3 teeth), moderate group (4-7 teeth), and severe group (≥8 teeth) based on the number of missing teeth. The salivary sIgA and peripheral blood Hb levels of children with different degrees of dental caries were compared. Pearson correlation analysis was used to evaluate the correlation between the number of missing teeth and salivary sIgA and peripheral blood Hb levels. Multivariate logistic regression analysis was used to evaluate the influencing factors of dental caries in children.Results:The salivary sIgA and peripheral blood Hb levels in the observation group were lower than those in the control group, and the differences were statistically significant (all P<0.05). There were 28 cases in the mild group, 50 cases in the moderate group, and 28 cases in the severe group, respectively. There were statistically significant differences in salivary sIgA and peripheral blood Hb levels among children with different severity of dental caries. As the severity of the disease increased, salivary sIgA and peripheral blood Hb levels showed a decreasing trend (all P<0.05). Pearson correlation analysis showed that the number of missing teeth was negatively correlated with salivary sIgA and peripheral blood Hb levels ( r=-0.572, -0.584; P<0.001). Multivariate logistic regression analysis showed that salivary sIgA ( OR=0.660, 95% CI: 0.463-0.941) and peripheral blood Hb ( OR=0.680, 95% CI: 0.505-0.916) were protective factors for the occurrence of dental caries in children (all P<0.05). Conclusions:Salivary sIgA and peripheral blood Hb levels in children with dental caries are low and negatively correlated with the severity of the disease.