OBJECTIVES: To determine the reference value of blood serum alkaline phosphatase of adult according to related age, sex, season and region. METHODS: In the research, totally 3742 people were conducted. The research was implemented and supported by central laboratory of Biomedical school, HSUM, “Mobio” laboratory of Korea and “Mega” laboratory. The research of serum alkaline phosphatase was made by the kinetic method which is confirmed by IFCC and used the liquid reagent of Roche Hospitex diagnostics and Human firm. The research result was statistically analyzed with standard programming the SPSS statistic. RESULTS: The mean value of blood serum alkaline phosphatase activity of adult with confidence interval P = 0.95, the mean value was for the male 81.78±0.48, (n=1597) U/L and for female 76.99±0.41 (n=2145) U/L. While determining the Interval for reference value of blood serum alkaline phosphatase, interval was for male  51.08-112.47 U/L8 U/L and for female 39.77-114.21U/L.  Blood serum alkaline phosphatase activity of adult Mongolian have dependence of sex (p<0.0001) and it was high for male. Also, serum alkaline phosphatase activity is varying (p<0.0001, r=0.102) depending on age. There is no dependence of activity of serum (p=0.43) appeared by region.  CONCLUSIONS: Mean value of serum alkaline phosphatase activity is for people 70.50±0.63 U/L and minimum limit of reference value is 40.09-116.72U/L.The activity of serum alkaline phosphatase has deference from age and sex with confidence interval (p=0.0001). For male high, for female low, weak direct dependence from age (r=0.102) and strong direct dependence from sex were discovered.