Objective: To explore the association between dietary inflammatory index (DII) and elevated blood pressure among primary school students, and to analyze the mediating role of body mass index (BMI) in this association, so as to provide a scientific basis for the early prevention of childhood hypertension and dietary guidance. Methods: Research conducted based on the Ma anshan Child Growth Cohort in Anhui Province. From April to June 2024, 4 057 primary school students were selected as study subjects using a multi stage cluster sampling method. Dietary information was collected via Semi quantitative Food Frequency Questionnaire to calculate the DII score. BMI was obtained by measuring students height and weight. Elevated blood pressure was defined based on the Blood Pressure Reference Standards for Children Aged 3-17 Years. Logistic regression was used to analyze the association between DII scores and the risk of elevated blood pressure, and the Bootstrap method was employed to test for mediating effects. Results: The detection rate of elevated blood pressure among primary school students was 10.1% (408 cases). Multivariate Logistic regression analysis showed that, after adjusting for covariates such as gender and age, for each standard deviation increase in the DII score ( s =1.94), the risk of elevated blood pressure increased by 15% ( OR =1.15, 95% CI =1.04- 1.28 , P <0.05). Compared with the lowest quartile group of DII scores ( Q 1), students in the highest quartile group ( Q 4) had a 1.31-fold higher risk of elevated blood pressure ( OR =1.31, 95% CI =1.00-1.76, P <0.05). Restricted cubic spline results indicated a linear dose response relationship between DII scores and the risk of elevated blood pressure( P nonlinear =0.13). The mediation analysis revealed that BMI played a partial mediating role in the association between DII scores and elevated blood pressure. The mediation effect value was 0.06 (95% CI =0.04-0.08), accounting for 44.64% of the total effect. Conclusions DII scores are associated with elevated blood pressure among primary school students in Ma anshan City, and BMI plays a partial mediating role in this association. Promoting an anti inflammatory dietary pattern and weight control in early childhood should be emphasized to reduce the incidence of hypertension among primary school students.