A mutant with small crinkled leaves were discovered in the progeny of the genomic DNA of island cotton (Gossypium barbadense L.cv.Hai7124 ) introduced into the upland cotton (G. hirsutum L. cv. Shiyuan321). Compared with the normal cotton plant, the leaves of the mutant were smaller and the stem was thinner, but it can flower and set bolls normally. Microscopic observation showed that cells of the mutant leaf epidermis were significantly larger than that of the wild type plant. The result of genetic analysis indicated that the mutant phenotype was controlled by a dominant allele that may have homologous lethal effect. The endogenous hormone contents showed that the IAA and ZR contents in apical buds were obviously higher in the mutant than that in the wild type plant. It is suggested that the abnormal contents of IAA and ZR in the mutant result in the phenotypic mutation.