In this experiment,the Welsh onion callus was treated by adding colchicines into the culture medium and dipped in colchicines solution.It resulted that both the two methods could effectively induce the tetraploid cells,but the former one was better in not only inducing rate but also operation.Adding 0.08% colchicines into medium for 4 days could obtain better induction effect with 26.0% of the doubling rate.