Objective To compare the clone forming capacity between keloid fibroblasts (KFs) and normal dermal fibroblasts (NFs), and to explore whether there are pathological stem cells in keloid and the role of keloid stem cells on the mechanism of keloid formation. Methods Primary cells were obtained from keloid tissue and normal dermis respectively through enzyme digestion method, and then were cultured under low-density conditions of 4 000/dish. Two weeks later, the clone formation and morphology were determined. Results Under low-density culture conditions, clones were formed in both KFs and NFs. KFs formed distinct and dense clones while NFs formed loose and fewer ones. KFs exhibited higher clone forming efficiency (CFE) of (0.80±0.21)%than NFs with CFE of (0.18±0.06)% (P<0.05). Conclusion With low-density culture, keloid fibroblasts possess higher level of cloning capacity than normal dermal fibroblasts, which suggests pathological stem cells may exist in keloid tissues.