Full‐visible‐spectrum emission phosphors are promising candidates for next‐generation white light‐emitting diodes (WLEDs), overcoming the complex and high costs of traditional mixed phosphors. However, their practical application is hindered by low luminescence efficiency. In this regard, we develop a generalization strategy that involves creating heterostructure interfaces to prevent the detrimental energy transfer process, thereby boosting efficiency. The SrLiPO4/Sr9MgLi(PO4)7:Eu2+ single‐grain phosphors prepared in this work have achieved remarkable full‐visible‐spectrum emission efficiency, with record internal and external quantum efficiencies of 76.1% and 56.2%, respectively. The WLEDs encapsulated with this phosphor feature a high color rendering index (~93.9), a low correlated color temperature (~3100 K), and stable color performance, indicating that the as‐synthesized single‐grain phosphor is an excellent candidate for healthy full‐visible‐spectrum lighting. This innovation is expected to accelerate the development of full‐visible‐spectrum phosphors technology and inspire the creation of more efficient and versatile luminescent materials in the future.