Photocatalytic overall water splitting (POWS) is a promising approach for solar-to-hydrogen conversion. For achieving this target, it is urgent to develop efficient photocatalysts. Constructing a heterojunction and loading a cocatalyst are two effective strategies for enhancing POWS. However, how to achieve the cooperation of loading the cocatalyst site with the charge separation of a heterojunction remains a huge challenge. Herein, we present an ingenious method: precisely assembling a H2O2-producing cocatalyst CoO on Tb4O7/CN. Assembling CoO on CN of Tb4O7/CN improves the photoinduced electron-hole pair separation and promotes the POWS performance. Inversely, engineering CoO on Tb4O7 leads to production of Co, deactivating POWS performance with a H2-evolution rate 5.2 times lower than that of Tb4O7/CN. Furthermore, we precisely assemble CoO on the CN section of Pt-oriented Pt-Tb4O7/CN. The bioriented CoO and Pt cooperatively promote photogenerated carrier separation. Consequently, the prepared Pt-Tb4O7/CN-CoO exhibits spectacularly high POWS activity. The H2-evolution rate reaches 450 μmol h-1 g-1, which is about 9.4 times higher than that of the initial Tb4O7/CN. The apparent quantum yield (AQY) for H2 evolution at 420 nm reaches 14.1%, surpassing those of most reported CN-based photocatalysts. This work offers an approach to precisely load cocatalysts on heterojunctions. These findings provide insights for designing cocatalyst-decorated heterojunctions for POWS.