Separation of high‐density suspension particles at high throughput is crucial for many chemical, biomedical, and environmental applications. In this study, elasto‐inertial microfluidics is used to manipulate ultra‐high‐density cells to achieve stable equilibrium positions in microchannels, aided by the inherent viscoelasticity of high‐density cell suspension. It is demonstrated that ultra‐high‐density Chinese hamster ovary cell suspension (>26 packed cell volume% (PCV%), >95 million cells mL−1) can be focused at distinct lateral equilibrium positions under high‐flow‐rate conditions (up to 10 mL min−1). The effect of flow rates, channel dimensions, and cell densities on this unique focusing behavior is studied. Cell clarification is further demonstrated using this phenomenon, from 29.7 PCV% (108.1 million cells mL−1) to 8.3 PCV% (33.2 million cells mL−1) with overall 72.1% reduction efficiency and 10 mL min−1 processing rate. This work explores an extreme case of elasto‐inertial particle focusing where ultra‐high‐density culture suspension is efficiently manipulated at high throughput. This result opens up new opportunities for practical applications of high‐particle‐density suspension manipulation. Elasto‐inertial microfluidics is used to manipulate ultra‐high‐density Chinese hamster ovary cells based on the inherent viscoelasticity of the high‐density suspension. Stable equilibrium positions in microchannels are achieved without the addition of fluid elasticity enhancers. As a practical application, high‐throughput cell clarification is demonstrated, from 29.7 packed cell volume% (PCV%) to 8.3 PCV% with overall 72.1% reduction.