The purpose of this study was to investigate the relationship between obesity indices, nutritional knowledge, nutritional intake status, and some blood parameters in obese middle-school students. Anthropometric measurement, 24-hour recall for dietary intake, blood analysis and Questionnaire response including nutritional knowledge, nutritional attitude, and self-satisfaction were conducted in 42 obese middle-school students (28 male and 14 female) participated in the nutritional camp program carried by Bucheon district public health center in Kyunggi-do. The mean age of subjects was 13.9 years. The average body weight, BMI, obesity index, WHR and percent body fat were 75.5 kg, 29.1 kg/$m^2$, 30.1, 0.89 and 33.3% in male subjects, and 67.8 kg, 27.5 kg/$m^2$, 25.3, 0.81 and 34.6% in female subjects. The average nutritional attitude, the self-satisfaction and the nutritional knowledge scores were no significant difference between male and female subjects. Average intake of energy were 85.5% of RDA in males and 98.1% of RDA in females. The percentage of energy from fat was higher in both male (29%) and female (26%) subjects than recommended level. Calcium, iron, zinc, vitamin A, vitamin B$_2$, vitamin C, niacin and folate intakes were below the RDA for them. In the results of correlation analysis, body weight, BMI and obesity index were positively correlated with systolic blood pressure and cholesterol intake. There was a negative correlation between percent body fat and nutritional knowledge. Body weight was negatively related to HDL-cholesterol, whereas it has positive relation with RBC, hemoglobin and hematocrit. BMI and obesity index were negatively related to HDL-cholesterol, but positively related to RBC, respectively. WHR showed positive relationship with serum GPT, glucose and MCV.