The present study measures the nutritional status and the blood pressure to assess their relationship in a group of children and adolescents in the Hainan province, China. A total of 5,456 students aged 7 to 18 years were recruited from 10 public schools in Hainan province of South China during the period March 2009 to December 2009. Height, weight, systolic blood pressure, and diastolic blood pressure were measured by health-care professionals. Body mass index (BMI) was calculated and used to define thinness, overweight, and obesity according to the existing standards. Prevalence of thinness, overweight, obesity, pre-hypertension, and hypertension was computed, and logistical regression model was used to examine the association of BMI with elevated blood pressure. A high prevalence of thinness was observed in male and female children and adolescents (34.0% and 34.3%, respectively). The percentage of overweight and obesity was 2.7% and 1.3%, respectively. Pre-hypertension and hypertension were detected in 3.9% and 3.3% children and adolescents, respectively. Multivariate logistical regression analysis showed that obesity was positively associated with both pre-hypertension and hypertension, with adjusted odds ratio of 1.44 (95% confidence interval (CI)01.08-1.92, P00.014) and 2.00 (95%CI01.53-2.60, P< 0.001) compared to normal weight students. Overweight was also associated with pre-hypertension and hypertension. However, no significant association between thinness and prehypertension and hypertension was found. In conclusion, this study showed that thinness, especially mild thinness, was a major public health problem among children and adolescents in Hainan province of South China. Overweight and obesity were strongly associated with pre-hypertension and hypertension among studied students.