Bi-0/p-BiOI/n-CdS was first designed to be applied to hydrogen evolution by water splitting. UV-vis diffuse reflectance spectroscopy (DRS) tests show that Bi-0 has an surface plasmon resonance (SPR) absorption peak at 428 nm. Theoretical calculations show that electrons generated in Bi were injected into BiOI. Due to the SPR effect of Be, both electron transfer kinetics and optical absorptivity were improved. Be also worked as a medium for storing and transferring electrons. Tauc plots and M-S tests show that Be has a band structure similar to semiconductors, indicating that Be exhibits semiconductivity. Therefore, two continuous heterojunctions Bi-0/p-BiOI and p-BiOI/n-CdS were formed. Finally, the H-2 and O-2 evolution active sites were spatially separated, thus alleviating the recombination of carriers and photocorrosion of CdS. Collectively, Bi-0/BiOI and CdS were combined to construct an SPR-enhanced double heterojunction structure. As a result, a hydrogen production efficiency of 31 mmol h(-1) was achieved.