Abstract: Objective To study the safety of arsenic using in children with acute promyelocytic leukemia(APL). Methods Fifteen children with APL diagnosed in our hospital from March 16, 2016 to May 1, 2018 were enrolled. The arsenic concentrations in different tissues including blood, urine, hair and nail, were measured during different treatment timepoints, and adverse reactions were observed to evaluate the safety of arsenic using in children with APL. Results All blood arsenic concentrations in children with CCLG-APL 2016 protocol were within the effective range of (10-100) ng·mL-1 during induction, consolidation and maintenance therapy, except for two cases were 121.3 ng·mL-1 and 9.46 ng·mL-1 during consolidation, respectively. After six months of discontinuation, the arsenic concentrations of blood and urine, with a level of 1.7 ng·mL-1 and 40.4 ng·mL-1, were reduced to normal levels as those before treatment, between which there was no significant difference (P>0.05). Arsenic concentrations in hair and nail peaked at the time of drug withdrawal and gradually decreased to the level before treatment after six months of discontinuation. In addition, it showed that blood arsenic concentration was positively correlated with urine (r=0.778, P<0.001), hair (r=0.641, P<0.001) and nail (r=0.655, P<0.001) arsenic. Arsenic concentration in urine with hair (r=0.622, P<0.001), and nail (r=0.688, P<0.001) were also positively correlated. And arsenic concentration in hair was positively correlated with nail (r=0.847, P<0.001). Up to now, with a longest follow-up period of 25.5 months and the average follow-up time of (12.2±7.8) months, the short-term response of arsenic disappeared after symptomatic therapy or arsenic reduction, and no chronic side effects of arsenic were observed. Conclusion Through the detection of arsenic concentration in different periods and different tissues, it was found that the blood arsenic concentration could be maintained within the effective concentration range in each treatment stage, and the arsenic concentration in blood, urine, hair and nails gradually decreased to normal after six months of discontinuation. The use of arsenic in children with APL is safe, but it still needs long-term follow-up.