This study was aimed to investigate the genetic characteristics of human acute lymphoblastic leukemia cell line Molt-4, and evaluate its application in measuring telomere length by Flow-FISH. Molt-4 cell line was cultured in suspension and subcultured regularly. Eight different passages of Molt-4 cells in exponential stage were selected.The growth curves were drawn by cell counting method, meanwhile calculating the population doubling times of cells,DNA ploidies were determined by flow cytometry,karyotypes were analyzed by G-banding and telomere lengths were measured by Southern blot. The results showed that the population doubling time of Molt-4 cell line was (1.315 ± 0.062) d, DNA ploidy index was (2.085 ± 0.0093) , and the telomere length was (32.05 ± 5.27) kb. There were no significant difference among different passages (P = 0.931,0.888 and 0.935 separately). The karyotypes showed that the chromosome numbers of Molt-4 cell line were from 91 to 99 in different metaphases, and the majority of them were hypertetraploid, and stable and recurrent structural abnormalities of chromosomes could be kept. It is concluded that the stable genetic characteristics and the longer telomere length of Molt-4 cell line makes it be a feasible control cells in measurement of telomere length by Flow-FISH.