Photocatalytic water splitting holds huge potential to meet the current challenges of energy and environments. Among them, polymeric carbon nitride (CN) has drawn much attention as a promising metal-free photocatalyst. As it is known, a number of promising co-catalysts have been developed to improve catalytic reactions, Pt nanoparticles is still among the best co-catalysts for CN in photocatalytic H-2 evolution, due to the suitable Fermi level to transfer excited electrons and the low overpotential for H-2 reduction. Herein, we report the interface engineering of urea derived bulk CN and Pt co-catalyst by using a small portion of N-doped carbon (N-C) as a transition layer with a boosted photocatalytic activity up to 7 times. It was revealed that the activation energy of the Pt co-catalyst for water reduction was lowered in the presence of N-C, and the intimate interaction between CN and N-C, ascribing to the similar elemental composition and crystal structure, promoted the efficient separation and migration of charge carriers. This study may open a new avenue to develop CN-based photocatalysts for solar fuel conversion with even higher activity by photocatalyst/co-catalyst interface engineering.