Аннотация:The ratio of branching fractions of B+c→B0sπ+ and B+c→J/ψπ+ decays is measured with proton-proton collision data of a centre-of-mass energy of 13TeV. The data were collected with the LHCb experiment during 2016--2018, corresponding to an integrated luminosity of 5.4fb−1. The B0s mesons are reconstructed via the decays B0s→J/ψϕ and B0s→D−sπ+. The ratio of branching fractions is measured to be B(B+c→B0sπ+)/B(B+c→J/ψπ+)=91±10±8±3 where the first uncertainty is statistical, the second is systematic and the third is due to the knowledge of the branching fractions of the intermediate state decays.