The immature inflorescence of Miscanthus floridulus were used as explants to establish the regeneration system in vitro. The results indicate that the best medium for callus induction was MS medium with 4.0 mg/L 2,4–D, 0.1 mg/L 6–BA, for bud differentiation was MS medium with 2.0 mg/L 6–BA and for plantlets rooting was MS medium with1.0 mg/L IAA, 0.1 mg/L IBA and 1.0 mg/L CCC. The effects of different concentrations of colchicine on polyploid induction were investigated in vitro. The results indicate that the induction rate of polyploidy in the treatment with 1 000 mg/L colchicine solution for 72 h reached 12.48%. The morphological characteristic, nuclear DNA contents and chromosome karyotype of the regenerated plantlets showed the inducted plantlets were tetraploid.