Objective To investigate the association of alkaline phosphatase (ALP) with metabolic syndrome (MS) and nonalcoholic fatty liver disease (NAFLD) in Chinese adults. Method A retrospective crosssectional study was performed. A total of 2638 subjects (2010 men, range of age: 19-92 years; 628 women, range: 21-92 years) who underwent annual health examination between January 1 and December 31 of 2009 were recruited from the Department of Health Management in the Aerospace Center Hospital, Beijing. The subjects who had the evidences of acute liver damage or chronic viral hepatitis B and C, renal failure, congestive heart failure, fracture, pregnancy, consuming alcohol and smoking were excluded. The diagnosis of fatty liver was based on abdominal ultrasonography. MS was defined according to the National Cholesterol Education ProgramAdult Treatment Panel III (NCEPATPIII) criteria modified for Chinese subjects. Results The prevalence of NAFLD and MS were 28.0% and 40.1% in men, 21.8% and 32.6% in women, respectively. After adjustment for age and liver enzymes, a strong associations of both genders with NAFLD and MS were found by multivariate logistic regression analysis. Stratified by interval of age of 5 years old as subgroup, the mean values of serum ALP level were significantly increased along with the increased age from 4564 years old in women, whereas there was no significant change for the mean values of serum ALP level among the age between 1992 years old in men. By binary logistic regression analysis, ALP level closely associated with NAFLD and MS in women (P<0.001). On the contrary, there was no significant correlation between ALP level and NAFLD and MS in men (P>0.05). In women, the cutoff value for identifying NAFLD was 57.1 IU/L by receiver operating characteristic (ROC) curve analysis, and the cutoff value for MS was 57.0 IU/L. Conclusion ALP should be a new comarker for the diagnosis of NAFLA and MS in women. Menopause of women may be a critical cause for the association of ALP with NAFLD and MS.