Chromosome doubling of interspecific hybrid between Curcuma alismatifolia and C. aurantiaca had been done by dropping 0, 400, 800,1,200 and 1,600 mg l-1 colchicine on shoot tips one drop per explants. By using fl ow cytometry, we found that the explants treated with 800 and 1,200 mg l-1 colchicine produced tetraploid shoots about 28.83 and 24.15% respectively. The 4x plants have more compact inflorescences, thicker bract, thicker dark green leaves but shorter inflorescences and leaves than those of 2x plants. 2x hybrids produced no pollen whereas 4x plants produced none to few pollen.Fruit setting is not occurred when pollinated allopolyploid pollen on C. alismatifolia. On the other hand, the seeds from backcrossed of 4x female and pollen of C. alismatifolia germinate and grow properly.