In this study, we address the intrinsic limitations of conventional exciplex hosts in organic light-emitting diodes (OLEDs), which are typically formed by physically blending p-type and n-type materials and often suffer from phase separation arising from mismatched solubility under solution-processing conditions. To overcome these challenges, an ambipolar macromolecular exciplex host was rationally designed and synthesized by integrating both donor and acceptor moieties within a macromolecular framework. This molecular engineering strategy effectively suppresses nano- and microscopic phase separation while enabling stable exciplex formation, leading to characteristic exciplex emission centered near 460–470 nm. Compared with conventional binary exciplex systems, the macromolecular host exhibits improved photophysical stability and enhanced device reproducibility in OLEDs, highlighting its potential as a stable, solution-processable exciplex host.