Objective: To investigate the doseresponse relationship between the risk of elevated blood pressure and body mass index (BMI) in primary and secondary school students in Shibei District, Qingdao, so as to provide a reference for precise interventions of elevated blood pressure. Methods: Statistical analysis was conducted on the health examination data of 92 091 primary and secondary school students in Shibei District, Qingdao, in 2022. Overweight and obesity were assessed using the standards from the Screening for Overweight and Obesity among Schoolaged Children and Adolescents, and blood pressure levels were evaluated using the Reference of Screening for Elevated Blood Pressure among Children and Adolescents Aged 7-18 Years. The relationship between BMI and elevated blood pressure was examined using analysis of variance, Chisquare test, multifactorial Logistic regression, and a combination of restricted cubic spline after data cleaning. Results: Based on the standardized scores under different age and gender, BMI was classified into 5 categories. Compared with the group of BMIZ scores 0-<1, the risk of developing high blood pressure gradually decreased with BMIZ scores (OR=0.55, 0.53, P<0.05). Conversely, the risk of developing high blood pressure increased with increasing BMIZ scores (OR=1.90, 3.71, P<0.05). Stratified analyses showed that BMI was positively associated with elevated blood pressure by gender (male, female), age (aged 7-8, 9-11, 12-14, 15-16), and waisttohip ratio (≤0.83, >0.83) (OR=1.18, 1.19, 1.15, 1.22, 1.19, 1.18, 1.19, 1.18, P<0.01). There were multiplicative interactions between BMI and gender, between BMI and age, between BMI and waisttohip ratio (OR=1.53, 1.08, 2.31, P<0.01). Restricted cubic spline analysis showed that as BMI levels increased, the risk of developing elevated blood pressure showed a nonlinear increasing trend in both the 7yearold and the 10 to 16yearold (χ2=27.56, 10.69, 6.10, 27.26, 18.32, 25.71, 10.53, 6.14, P<0.05). Conclusions The risk of elevated blood pressure in primary and secondary school students increases with BMI, showing a nonlinear doseresponse relationship. The blood pressure should be monitored regularly, and comprehensive and effective measures should be implemented to control elevated blood pressure in children and adolescents.