Abstract: The α decay half-lives of the ^191-220At isotope chain are calculated by Gamow-like model, and are also performed by the generalized Royer formula and the generalized UDL formula. The comparison between the theoretical results and experimental values show that the Gamow-like model with only Coulomb and centrifugal potentials can reproduce the experimental data well, and the two extended semiempirical formulas can also describe the α decay half-life of the At isotopes chain well. Based on this situation, the α decay half-life of the unknown nucleus ^184-190At are predicted by the Gamow-like model and the two semiempirical formulas, which hopes that the results can provide some references for the experimental synthesis of new nuclides.