Abstract: Objective To explore changes and of levels of serum ceruloplasmin (CER) in patients with Alzheimer's disease(AD) and their indications. Methods A total of 1,086 AD patients were screened in this trial.Finally 125 patients with AD were selected and randomly divided into mild (28 cases),moderate(42 cases) and severe (55 cases) groups according to Clinical Dementia Rating Scale(CDR).Meanwhile,40 healthy elderly people were also selected as the control group.The levels of their serum CER were tested at fasting state.The differences of serum CER levels among all groups were done to explore the dynamic regulation of serum CER levels in AD patients and to analyze the correlation between the severity of dementia and serum CER levels. Results Levels of CER of patients in moderate and sever groups were significantly lower than those in control group(0.17±0.48 vs. 0.24±0.54;0.15±0.41 vs. 0.24±0.54).There's a positive correlation between the level of CER and scores of Mini-mental State Examination (MMSE) according to the multiple linear regression analysis (r=0.473,P=0.014).There were interactions between severity of dementia and level of serum CER that patients with moderate dementia had the highest score in The Brief Psychiatric Rating Scale (BPRS) when the level of serum CER reached approximately to 0.17 g/L. Conclusion The abnormality of serum CER levels in AD patients may correlate to AD progression.There's a positive correlation between the level of serum CER and the severity of cognitive impairment that the lower the level of CER,the more severe the cognitive impairment was.There were interactions among severity of dementia,the level of serum CER and patients' behavioral and psychiatric symptoms.