To investigate the changes in motor function, sensory function, cognitive function, and fine behavior in male and female mice during natural aging. Methods: C57BL/6J mice aged 3 months and 21 months were subjected to assessments of motor function (open-field test, rotarod test, balance beam test, and gait analysis), sensory function (Von Frey test), cognitive function (novel object recognition test), and fine behavior analysis in home cages to compare the effects of natural aging on the behavior of male and female mice. Results: In motor function tests, compared with younger mice of the same sex, elderly female mice exhibited a significant decrease in both the distance traveled and movement speed in the open field (P<0.05), while no significant changes were observed in elderly male mice. In the rotarod test, both elderly male and female mice showed a significant decline in motor balance (P<0.01). In the balance beam test, the motor balance and coordination of elderly mice deteriorated, with a more pronounced decline in elderly male mice (P< 0.0001). In the gait analysis, both elderly male and female mice demonstrated a reduction in gait symmetry (P< 0.001). Regarding sensory function, the pain thresholds of both elderly male and female mice were significantly higher than those of younger mice of the same sex (P<0.0001), indicating a diminished response to noxious stimuli. In terms of cognitive function, elderly male and female mice lost the preference for exploring novel objects that was observed in younger mice. The results of fine behavior tests in home cages revealed that, compared with younger mice of the same sex, elderly female mice showed a 9.14% decrease in spontaneous motor behavior and a 38.05% decrease in exploratory behavior, while self-care behavior increased by 15.52%. In elderly male mice, spontaneous motor behavior and exploratory behavior decreased by 46.50% and 9.59%, respectively, while self-care behavior increased by 2.36% . Compared with male mice, female mice spent a greater proportion of time on exploratory and spontaneous motor behaviors and engaged in less self-care behavior overall. Conclusion: As mice age naturally, their motor, sensory, and cognitive functions decline, exhibiting certain sex-dependent characteristics.