Postoperative cognitive dysfunction (POCD) refers to the difficulties of orientation, cognition, communication, memory and abstract thinking of patients after anesthesia and surgery. And/or accompanied by the decline of the ability in social activities, such as the change of personality, social ability of language and behavior, cognitive function and life skills. POCD is a common complication of central nervous system in elderly patients after operation, with an early incidence of about 21% and a long-term incidence of about 35% . According to the current research on Alzheimer's disease (AD) and POCD in the elderly, it has been found that they have similar pathological basis and some homologous related genes. Altogether, POCD is closely related to molecular pathway neuropsychiatric diseases (such as dementia, depression and Alzheimer's disease). Researchers have come up with various hypotheses to reveal the underlying mechanisms of POCD, including neuritis, oxidative stress, autophagy disorder, synaptic dysfunction, and lack of neurotrophic support. To date, apart from evaluating with scales, CT Scan and EEG analysis, there is neither exact biomarkers for monitoring and diagnosing POCD, nor clear relationships between specific Brain Metabolomic Characteristics, EEG changes and diagnosis of POCD, so that the diagnosis of early POCD only stays in the evaluation of clinical symptoms and scales. Therefore, our study aims to provide an effective basis for early diagnosis and treatment of clinical POCD through multivariate analyses of clinical scales combined with Brain Metabolomic Characteristics, EEG analysis of patients.