Abstract: An Arabidopsis thaliana mutant k60 with a chlorosis symptom was obtained by screening an ethyl methane sulphonate (EMS) mutagenized mutant population. This mutant displayed a phenotype of yellow leaf, slow growth and reduction of chlorophyll content. Genetic analysis indicated that the mutant phenotype was recessive and controlled by a single gene. k60 was mapped to a region of 231 kb between molecular markers CH5-6.043 and CH5-6.127 on chromosome 5 by genetic mapping. The results in this study lay the basis for the identification of the mutant gene, and provide a new material for the study of the function of chlorosis genes in Arabidopsis.