Abstract: Based on the original material of 14C-labelled Ba14CO3,14C-labelled 1,2,4-triazol was synthesized by means of 4 steps reaction,which radioactive strength,specific activity,radiochemical purity and radiochemical yield were 5.813 1 mci,15.534 7 μci/mg,more than 99% and 84.21%,respectively.According to the methods reported to synthesize myclobatanil,14C-labelled myclobutanil was made from 4-chlorophenylacetonitrile through substitution and condensation.Its radioactive strength,specific activity,radiochemical purity and radiochemical yield was 0.556 6 mci,2.53 μci/mg,more than 96% and 85.4%,respectively.The uptake,translocation and distribution of myclobutanil in wheat seedling at 2~3 leaves stage were studied by radioactive trace experiment.The result showed that radioactivity in the treated wheat roots dropped from 59.88% to 24.87%,and the accumulation of radioactivity in the stem base and leaves respectively increased from 14.18% and 1.19% to 19.47% and 33.75% after dipping the roots into 14C-myclobutanil solution for 6~120 h.14C-myclobutanil could be absorbed and translocated upwards to the top of wheat seedling readily.The distribution and accumulation of 14C-myclobutanil in wheat leaves were positively correlated with treatment time of dipping the root into the chemical solution,with a steady increase in radioactivity from 2.94×10-6 μci at 6 h to 322.72×10-6 μci at 120 h.Autoradiograph experiment indicated that 14C-myclobutanil could be absorbed and distributed in whole seedling at 120 h after treating the roots.