TaN is one of the most promising photocatalyst candidates for solar water splitting, but it still remains challenging to achieve overall water splitting TaN-based photocatalysts regardless of whether it uses a one step or two step method. Here we will address the relatively poor photocatalytic proton reduction of TaN with an effort for the promotion of charge separation barium modification. One-pot nitridation of barium nitrate-impregnated TaO precursor was adopted here for the synthesis of TaN accompanied with the creation of a TaN/BaTaON heterostructure and surface passivation. Due to the synergetic effect of the improved interfacial charge separation and the decreased defect density, the photocatalytic H evolution rate of barium-modified TaN is effectively promoted. Encouraged by this, a visible-light-driven Z-scheme overall water splitting system was successfully constructed by using the barium-modified TaN as a H-evolving photocatalyst, together with a PtO /WO and IO/I pair as an O-evolving photocatalyst and a redox mediator, respectively.