  A charge order (CO) with a wavevector
$\mathbf{q}\simeq\left(\frac{1}{3},0,0\right)$ is observed in infinite-layer
nickelates. Here we use first-principles calculations to demonstrate a
charge-transfer-driven CO mechanism in infinite-layer nickelates, which leads
to a characteristic Ni$^{1+}$-Ni$^{2+}$-Ni$^{1+}$ stripe state. For every three
Ni atoms, due to the presence of near-Fermi-level conduction bands, Hubbard
interaction on Ni-$d$ orbitals transfers electrons on one Ni atom to conduction
bands and leaves electrons on the other two Ni atoms to become more localized.
We further derive a low-energy effective model to elucidate that the CO state
arises from a delicate competition between Hubbard interaction on Ni-$d$
orbitals and charge transfer energy between Ni-$d$ orbitals and conduction
bands. With physically reasonable parameters,
$\mathbf{q}=\left(\frac{1}{3},0,0\right)$ CO state is more stable than uniform
paramagnetic state and usual checkerboard antiferromagnetic state. Our work
highlights the multi-band nature of infinite-layer nickelates, which leads to
some distinctive correlated properties that are not found in cuprates.
