Abstract: Decabromodiphenyl ether (BDE209) and its substituted product, decabromophenyl ethane (DBDPE) were measured in domestic indoor dust collected from eleven cities in Guangdong Province, including Shaoguan, Qingyuan, Heyuan and so on , to assess human exposure to BDE209 and DBDPE via indoor dust. DBDPE and BDE209 were detected in all samples, and the concentrations of DBDPE and BDE209 in indoor dust were 30.9-163,70 and 5.44-955ng/g, with an mean value of 3020 and 167 ng/g, respectively. Compared with correlated results from domestic and international studies , the DBE209 level in the present study was at the low end, while DBDPE was at the high end; the ratios of DBPDE/BDE209 were between 1.70 to 194 , indicating that DBDPE residue in Guangdong indoor dust has already surpassed that of BDE209. Average daily estimated intake of DBDPE via indoor dust was 0.72 ng/kg?day for adults and 14.5 ng/kg?day for young children, and the corresponding value for BDE209 was 0.040 ng/kg?day in adults and 0.80 ng/kg?day in children; the maximum daily estimated intake of DBDPE and BDE209 for children was 58.0 and 3.21 ng/kg?day, about 20 fold of that for adults. The results suggested that DBDPE and BDE209 may pose higher health risk to children than adults via contaminations in indoor dust.