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Precise determination of the Bc → tvt branching ratio provides an advantageous opportunity for under-standing the electroweak structure of the Standard Model,measuring the CKM matrix element IVcbl,and probing new physics models.In this paper,we discuss the potential of measuring the process Bc—τvτ with r decaying leptonically at the proposed Circular Electron Positron Collider(CEPC).We conclude that during the Z pole opera-tion,the channel signal can achieve five-cr significance with～109 Z decays,and the signal strength accuracies for Bc → τvτ can reach around 1％level at the nominal CEPC Z pole statistics of one trillion Z decays,assuming the total Bc → τvτ yield is 3.6 × 106.Our theoretical analysis indicates the accuracy could provide a strong constraint on the general effective Hamiltonian for the b→ crv transition.If the total Bc yield can be determined to 0(1％)level of accuracy in the future,these results also imply |Vcb| could be measured up to 0(1％)level of accuracy.