A special type of variation--the mixoploid variation, which had a great effect on the variation in the production of banana vitroplants, was reported for the first time. By means of examining chromosome, isozymes (EST, MDH, POX) and endogenous hormones (iPAs, IAA), the varied characters of the mixoploid varianties during the propagation in vitro when cultured as explant were investigated. The rate of the chromosome aberration in cells was characterized by starting at a much higher level and rising more rapidly in the preceding 15 subcultures as compared with the control. The rate of the isozyme variation was higher obviously than that of the control. The plantlets cloned in vitro from the mixoploid variant were also studied. The experiment showed that both the variant rates of chromosome and phenotype rose obviously. The mixoploid variant can cause the rate of variation to rise during the micropropagation.