Objective To explore the blood arsenic exposure levels of preschool children and analyze the factors of blood arsenic. Methods By the multi-stage cluster and simple randomized method, six districts of Shanghai City was chosen and the preschool children in the selected village were asked to fill in the questionnaire and have blood sampling. Inductively coupled plasma mass spectrometry(ICP-MS)was used to detect blood arsenic, of which the data was analyzed by multiple linear regression models. Marine fish, freshwater fish, freshwater shrimp and shellfish were grouped as follows:≤3 times per month, 1-3 times per week, and 4-6 times per week. Rice, noodles and milk were grouped as <50,50-100, and ≥100 g/d. Results 2 263 preschool children were recruited. The range of blood arsenic was 0.12-27.94 μg/L. The median (P25,P75) were 2.26(1.63,3.09) μg/L. Statistical analysis showed that the more intake of rice, wheaten food, and sea fish and shrimp, the more arsenic in children's blood(P<0.05). Whereas highter intake of freshwater fish and shrimp group showed decreased blood arsenic(P<0.05). Conclusion Most preschool children's blood arsenic levels(92.4%, 2 091/2 263) were at normal level (<5 μg/L). There was a positive correlation between blood arsenic concentration and the intake of rice, wheaten food, and sea fish and shrimp, while negative correlation with high freshwater fish and shrimp consumption.