The large‐scale synthesis of high‐quality boron nitride nanotubes (BNNTs) has attracted considerable interests due to their applications in nanocomposites, thermal management, and so on. Despite decades of development, efficient preparation of high‐quality BNNTs, which relies on the effective design of precursors and catalysts and deep insights into the catalytic mechanisms, is still urgently needed. Here, a self‐catalytic process is designed to grow high‐quality BNNTs using ternary W–B–Li compounds. W–B–Li compounds provide boron source and catalyst for BNNTs growth. High‐quality BNNTs are successfully obtained via this approach. Density functional theory‐based molecular dynamics (DFT‐MD) simulations demonstrate that the Li intercalation into the lattice of W2B5 promotes the formation of W–B–Li liquid and facilitates the compound evaporation for efficient BNNTs growth. This work demonstrates a high‐efficient self‐catalytic growth of high‐quality BNNTs via ternary W–B–Li compounds, providing a new understanding of high‐quality BNNTs growth.