Objective To explore the correlation of age-related hearing loss and cognition impairment in C57BL/6J mice by observing hearing, cognitive function and synapses. Methods C57BL/6J and CBA/CaJ mice were divided into 3 groups. The hearing and cognitive functions of each animal was tested. And the ultrastructure of synapses was simultaneously observed for C57BL/6J mice. Results The 24-26-week-old C57BL/6J mice developed moderate hearing loss while the 42- 44-week-old C57BL/6J counterparts suffered profound hearing loss. Whereas excellent hearing was maintained in 3 groups of CBA/CaJ mice within 44 weeks. During cognitive test, the performance of 42 -44-week-old C57BL/6J mice was significantly worse than CBA/CaJ mice. During probe test, the number of platform crossing of 42 - 44-week-old C57BL/6J mice was smaller than that of CBA/CaJ mice(0.5 ± 0.6 vs 1.9 ± 1.6; P ＜ 0.05 ). The 42 -44-week-old C57BL/6J mice had a wider synaptic cleft and a thinner postsynaptic density than the 24 -26-week-old C57 BL/6J counterparts [synaptic cleft: ( 19.4 ± 0.5 ) nm vs ( 1 1. 9 ± 0.7 ) nm; postsynaptic density:(15.2 ±0. 5) nm vs (27.8 ±2.0) nm; both P ＜0.05]. Furthermore, the degeneration of synapses in hippocampus CA3 area of C57BL/6J mice were clearly observed at 42 -44 weeks of age, but not seen in CBA/CaJ mice. Conclusion Age-related hearing loss might impact on the cognition impairment in C57 BL/6J mice.