[en] In this paper, we study the combined sensitivity of T2K-II and NOvA, the world leading long-baseline neutrino oscillation experiments, to CP violation in lepton sector. By operating until the year 2026, T2K-II is expected to collect a total exposure of 20×10²¹ protons-on-target. Meanwhile, NOνA experiment plan to expend the run up to 2024 for accumulating totally an amount of72×10²⁰protons-on-target. By combining T2K-II and NOνA with an ultimate constraint from reactor, the sensitivity to CP-violation is expected to exceed 4σ C.L. It is also pointed out that by reducing the systematic uncertainties of both T2K-II and NOνA to a level of 2 %, the sensitivity to CP-violation will significantly increase with a discovery possibility at 5σ C.L. significance for a particular range of true δCP. (author)