Gene amplification is the most frequent aberrance in the tumorigenesis and progression of various tumors, and double minutes (dmin) is one of the identifiable gene amplification cytogenetically.A lot of proto-oncogenes and chemo-resistance genes are localized on extrachromosomal dmin, it offers advantage for tumors growth and resistance to chemotherapy.In this manuscript, we first established several sub-clone cells with apparent difference in the number of dmin by infinite dilution.