Abstract: Objective　To investigate peripheral blood chromosome determination and chromosome karyotype analysis among high risk population.   Methods　A total of 850 high risk genetic counseling subjects were enrolled in the study，who underwent chromosome determination and chromosome karyotype analysis. Results　Among the 850 cases，there were 258 cases（30.35%）with chromosomal abnormalities. Of them，145 cases（56.20%）were mental retardation，86 cases（33.33%）were reproductive disorders，and 27 cases（7.75%） had a family history. Conclusions　The incidence rate of chromosomal abnormalities is quite high in high risk population，so it is very important for chromosome determination among high risk population，which can find the cause，improve the diagnosis and treatment level，improve population quality for eugenics，and reduce and avoid the occurrence of chromosomal diseases.

Key words: Chromosome determination, Karyotype analysis, High risk population