In order to establish a sensitive method for detecting cellular growth of fibroblasts. Three kinds of fibroblasts were used, including normal rat kidney (NRK), human embryo lung fibroblast cell (MRC-5) and normal human fibroblast(NF). In those cells, mitochondrion dehydrogenase together with phenazine methosulfate (PMS) reduces 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-［(phenylamino) carbonyl］-2H-tetrazolium hydroxide (XTT) and a water soluble and light brown formazan product is formed. Cell growth and viability were obtained by measuring the metabolic product and compared with the traditional 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. It was shown that three kinds of cells have different metabolic response to XTT. XTT method directly detected water soluble formazan product. Its sensitivity was higher than MTT. These results indicate that it is a simple, rapid, sensitive and stable method. XTT colorimetric method establishes a new detective method for keloid research of traumatic surgery.