Objective To investigate the current status of cognitive impairment and its influencing factors in patients with Alzheimer's disease (AD) and to explore effective intervention strategies. Methods A total of 380 patients with AD diagnosed in the Qingdao Central Hospital were retrospectively enrolled between January 2023 and January 2025. According to scores of Montreal Cognitive Assessment (MoCA), the patients were divided into a mild cognitive impairment group (21-25 points) and a moderate to severe impairment group (<21 points). The general clinical data in the two groups were collected. The influencing factors of moderate to severe cognitive impairment were analyzed by univariate and multivariate logistic regression analysis. Results Among the 380 AD patients, 157 cases (41.32%) had mild cognitive impairment, and 223 cases (58.68%) had moderate to severe cognitive impairment. Compared with the mild cognitive impairment group, the moderate to severe cognitive impairment group had a higher proportion of patients who were aged ≥ 75 years, engaged in physical labor, had a disease course of ≥5 years, and had moderate to severe atrophy on head CT examination (P < 0.05). Age ≥75 years, disease course ≥5 years, and moderate to severe atrophy on head CT were independent risk factors of moderate to severe cognitive impairment in AD patients (P<0.05). Conclusion Cognitive impairment is closely related to age, disease course and head CT manifestations in AD patients. Interventions targeting these key factors are expected to delay cognitive decline and improve patients' quality of life.