Abstract: In order to evaluate the validity of early nicotine conversion induced by 2-chloroethyl phosphonic acid in burley tobacco, the nicotine conversion in 3 burley cultivars and 1 improved cultivar from Hubei and Hainan treated with 2-chloroethyl phosphonic acid was studied and compared with the nicotine conversion in control leaves cured in the conventional way. The results showed that except Eyan1 cultivated in Enshi County of Hubei Province, all treated cultivars exhibited higher average nicotine conversion rate comparing with the control, and the average nicotine conversion rate and proportion of high converters in cultivar B21 were the highest; the results of converter identification of 3 cultivars in Enshi presented higher consistency between treated and control leaves than that in Hainan Province, and the number of converters in treated TN90 in Enshi and improved Eyan1 in Hainan were higher than that in control leaves. Breeding of non-converter by early induction and identification, the nicotine conversion rate in the progeny of cultivar Eyan1 decreased from 22.10% and 16.93% to 3.98%, and the proportion of converters, especially that of high converters reduced from 48% and 27% to 2%.