Acoustic graphene plasmons (AGPs) have an extreme level of field confinement and low loss in the mid-infrared and terahertz spectra, which have been applied for quantum effect exploration and ångström-thick material sensing. However, up to now, it is still a lack of exploration of the in-plane scattering of AGPs, though it is essential for the manipulation and utilization of ultraconfined optical field down to atomic level. In this work, by using scattering-type scanning near-field optical microscopy (s-SNOM), the mid-infrared AGPs, which are strongly scattered by atomic level height steps, were imaged in real-space. Particularly, even though the step height of the scatterer is four orders of magnitude lower than the incident free wavelength, strong scattering of AGPs still was achieved and can be attributed to larger reflectivity of AGPs than that of the traditional graphene plasmons (GPs). In addition, the scattering of AGPs by individual scatterers can be controlled via electrical back gating, in which a high fringe contrast up to about 82% was achieved. Our work suggests a feasible way to control extremely confined optical fields with atomic level height nanostructures, which can be used for ultra-compacted strong light-matter interactions, e.g. photodetector, biosensing, and strong coupling effects.