Objective To observe the changes of cognitive function and brain function in patients with chronic kidney disease (CKD). Methods Ten CKD patients with stage 3-4 diagnosed in Dongzhimen Hospital from January 2018 to January 2020 were selected as the observation group, and 19 subjects with normal renal function as the control group. The mini-mental state examination (MMSE) scale, auditory verbal learning test (AVLT) scale, digit span test(DST), animal fluency test (AFT) scale, trail making test part A and B (TMT A and B), and Alpine scale were used to evaluate the cognitive function and memory satisfaction of the two groups, and the resting-state functional MRI(rs-fMRI) scanning was performed to observe the differences in brain function between two groups. The clinical data were analyzed using SPSS statistics 20.0. Results In terms of cognitive function, compared with the control group, the scores of immediate recall, short-term recall and long-term recall of AVLT in the observation group were significantly decreased (P＜0.005), and the score of Alpine scale was also significantly decreased (P=0.024). In terms of brain function, the left hippocampal degree centrality (DC) of the observation group was significantly higher than that of the control group (P＜0.01); the functional connection between the left hippocampus and the middle frontal gyrus and precentral gyrus were decreased (P＜0.01), and the weakened functional connection was significantly negatively correlated with auditory short-term recall and long-term recall (P＜0.05).Conclusion Compared with people with normal renal function, CKD patients have a lower cognitive function, especially episodic memory function; in terms of brain function, CKD patients have higher DC of left hippocampus and lower functional connection between hippocampus and middle frontal gyrus and precentral gyrus,and this weakened functional connection is significantly negatively correlated with episodic memory function.