Abstract: To explore the distribution about genotype and allele frequencies of NcoI polymorphism in the CKMM gene in Han population in Northern China, and investigate what the genotypes were, PCR-RFLP was used to examine the genotype and allele frequencies of 306 unrelated healthy persons. Sequencing was used to analyze all three genotypes. X2 test was used to compare the frequencies between Chinese Han population and foreign population. The NcoI polymorphism was A/G. The allele frequencies were as follows: A=86%,G=14% . The genotype frequencies were A/A=74%, A/G=24%, G/G=2% and they were in Hardy－Weinberg equilibrium. Thesite of NcoI in the CKMM from Chinese Han population had polymorphism. No significant difference was detected in genotype and allele frequencies between men and women. There were significant differences between Chinese Han population and those in Europe and America, but no significant difference was detected between Chinese population and Korean population.