Novel BiSI promoted n-p-n double heterojunction multi-interface photocatalyst BiSI/MoS2/CdS was constructed. BiSI is applied to the photocatalytic hydrogen evolution. It possesses a small band gap and a strong optical absorption coefficient; therefore, the optical absorption scope and coefficient of MoS2/CdS have been effectively enhanced by compounding with BiSI. The continuous heterojunctions strengthened the function of the single junction and guided the carriers' transfer direction; thus, the redox reactions occur at spatially separated sites. The built-in electric field along the radial direction of the BiSI nanorod and MoS2 interlayer helps to transport carriers within the lifetime. Carrier dynamics is optimized by the multi-interface structure. In general, a new material BiSI is introduced to construct a multi-interface structure to optimize carrier dynamics, which resulted in a 46-fold increase in hydrogen production efficiency.