Children’s urine sample was digested with nitric acid and drop-wise added hydrogen peroxide. After pre-reduction with ascorbic acid-thiourea, the total arsenic in sample solution was formed arsine in a flow injection hydride generation system and then was detected by atomic fluorescence spectrometry. Calibration curve was established every day and blank correction should be made for each analysis. Detection limit was 0.03 μg·L-1. Analytical results of urine arsenic for 40 children sampling from Minhang District, Shanghai, were in the range of 0.5～1.5 μg·L-1, possibly due to the foodstuffs of seafood and is not harmful to the human health.