Ambient-pressure high- Tc superconductivity in doped boron-nitrogen clathrates La(BN)5 and

${\mathrm{LaH}}_{10}$ exhibits the near-room-temperature superconductivity, but the high fabrication pressure exceeding 200 GPa limits the possibility of its experimental research and application. To examine the feasibility of high-temperature superconductivity at ambient pressure in light-element compounds, we study the crystal structure, metallization, and electron-phonon interaction of $M{(\mathrm{BN})}_{5}$ ($M$ = La and Y) with ${\mathrm{LaH}}_{10}$-like clathrate configuration, based on the first-principles calculations. The result shows that adopting B and N to substitute H, the strong $s{p}^{3}$ hybridization between B and N greatly reduces the pressure to keep the dynamical stability. We predict that the strong electron-phonon coupling exists in $M{(\mathrm{BN})}_{5}$ and the ${T}_{c}$ values of $\mathrm{La}{(\mathrm{BN})}_{5}$ and $\mathrm{Y}{(\mathrm{BN})}_{5}$ reach 69 and 59 K at ambient pressure, respectively. As a result, the high-temperature superconductivity at ambient pressure in clathrate BN compounds has been proved theoretically, which provides a way to lower the work pressure of hydride superconductors.