  The XENON1T excess of keV electron recoil events may be induced by the
scattering of electrons and long-lived particles with MeV mass and high-speed.
We consider a tangible model composed of two scalar MeV dark matter (DM)
particles $S_A$ and $S_B$ to interpret the XENON1T keV excess via boosted
$S_B$. A small mass splitting $m_{S_A}-m_{S_B}>0$ is introduced and the boosted
$S_B$ can be produced by the dark annihilation process of $S_A S_A^\dagger \to
\phi \to S_B S_B^\dagger$ via a resonant scalar $\phi$. The $S_B-$electron
scattering is intermediated by a vector boson $X$. Although the constraints
from BBN, CMB and low-energy experiments set the $X-$mediated $S_B-$electron
scattering cross section to be $\lesssim 10^{-35} \mathrm{cm}^2$, the MeV scale
DM with a resonance enhanced dark annihilation today can still provide enough
boosted $S_B$ and induce the XENON1T keV excess. The relic density of $S_B$ is
significantly reduced by the $s$-wave process of $S_B S_B^\dagger \to X X$
which is allowed by the constraints from CMB and 21-cm absorption. A very small
relic fraction of $S_B$ is compatible with the stringent bounds on un-boosted
$S_B$-electron scattering in DM direct detection and the $S_A$-electron
scattering is also allowed.
