Objective To explore the damage mechanism of decabromodiphenyl ether on learning and memory ability，and to provide scientific reference for the formulation of occupational exposure prevention and control measures of decabromodiphenyl ether. Methods Neurotoxic effects of decabromobiphenyl （BDE-209） on learning and memory and hippocampal N-methyl-d aspartic acid （NMDA） receptors in adult rats were observed. A total of 32 SPF male SD rats were randomly divided into 4 groups with 8 rats in each group: solvent （peanut oil） control group and 250，500，1 000 mg/kg BDE-209 exposed group. Continuous tube feeding was administered once a day for 30 days. After exposure，the capability of spatial learning and memory of rats were tested by place navigation and spatial probe tests. RT-PCR was used to identify the mRNA levels of NMDA receptor subunits in the hippocampus in adult rats. Results During the same training time，compared BDE-209-treated rats in different dose groups with the solvent control rats，the times of founding the platform in the BDE-209-treated groups were prolonged in a dose-dependent manner，and the numbers of rats crossed the original platform decreased in a dose-dependent manner too，with significant difference （P < 0.05）. The mRNA expression levels of NR1，NR2B and NR2C subunits in hippocampus of rats exposed to BDE-209 were lower than those in control group. （P < 0.05）. The mRNA relative expression levels of NR1 and NR2B subunit decreased with the increase of BDE-209 exposure dose. Compared with the solvent control group，the mRNA relative expression of NR2A subunit in the hippocampus of rats in the exposed group was decreased. （P < 0.05）. Compared with the solvent control group，low dose group and medium dose group，the mRNA relative expression of NR2D subunit of NMDA receptor in high dose group was significantly decreased （P < 0.05）. Conclusion BDE-209 exposure resulted in decreased learning and memory ability in rats，which may be related to decreased mRNA expression of subunits of NMDA receptor in hippocampus..