Abstract: This study has introduced a simple microtechnique for obtaining metaphase chromosomes from cardio-blood of living rat.Through repeated experiments,we have confirmed that this culture method is effective and can be used.In the paragraphs of "results" and "discussion",we compared the effect of various factors,including different cultural time,PHA doses,pH values and heparin doses,on cell division and growth.Meanwhile,we have preliminarily determined the division cycle of rat lymphocytes,which is about 16 hours.