〔Abstract〕 To explore the changes in behavior and spatial memory of C57BL/6J female mice of differ- ent ages (youth , middle-aged , and elderly) . Methods C57BL/6J female mice were divided into female youth group (YG group) , female middle-aged group ( MG group) and female elderly group ( OG group) according to age. The Morris water maze test measured spatial memory ability , and the open field and elevated cross maze test observed activity level and anxiety level. Western blot was used to determine the protein expressions of CREB , CaMKⅡ(pan) and CaMKⅡ(p) in the hippocampus of the brain tissues of female mice in each group. Results Compared with the YG group , the weight of the MG group and the OG group significantly increased (P < 0. 01 , P < 0. 001) . Compared with the OG group , the third quadrant escape latency and the number of crossings in the YG group and MG group were shortened , and the difference was not statistically significant. Compared with the OG group , there was a statistically significant difference in the exercise speed in the open field of the YG group (P < 0. 01) , there was no significant difference in the movement speed in the open field of the MG group , the number of entries into the central zone significantly increased in the MG group ( P < 0. 05 ) , and there was no significant difference in the number of entries in the YG group (P > 0. 05) . Compared with the OG group , the YG group had a statistically significant difference in the elevated cross maze (P < 0. 05) , the MG group had no statistically signif- icant difference in the elevated cross maze , and the number of closed arm entries in the YG group and MG group significantly increased (P < 0. 001 , P < 0. 01) . Compared with the YG group , the relative expression level of CaMKⅡ(pan) in the OG group was statistically significant ( P < 0. 05 ) , while the relative expression level of CaMKⅡ(pan) in the MG group was not statistically significant ( P > 0. 05) . Conclusion With the increase of age , the weight of C57BL/6J female mice gradually increased , the activity level and desire to explore gradually de- creased , the spatial memory ability also declined , and the anxiety level and anxiety-like behavior increased. This study helps to reveal the effect of age on the activity level and cognitive function of females , and provides a refer- ence for studying cognitive and memory decline in older females.