beta-iron oxide hydroxide (beta-FeOOH) had been proven to be an effective co-catalyst during H-2 evolution reaction (HER) process. In this research, a BiOCl/beta-FeOOH heterojunction was successfully synthesized by a solid-state doping method. Then, the structure, composition, and photo-electrochemical properties of the prepared photocatalysts were studied. For the superior HER photocatalytic activity of ultrasmall beta-FeOOH nanoparticles (NPs) and the formation of the BiOCl/beta-FeOOH heterojunction, this heterojunction photocatalyst exhibited very superior photocatalytic performance in the HER process. Especially, when the amount of incorporated beta-FeOOH NPs was appropriate, the BFOH-2 possessed the highest photocatalytic activity in HER process, and the HER rate was about 16.64 mmol center dot g(-1)center dot h(-1) during illuminated time of 6 hours under visible light. When appropriate, ultrasmall beta-FeOOH NPs were implanted into the structure of BiOCl, the BiOCl/beta-FeOOH heterojunction interfaces would form for the existence of interfacial interactions. Therefore, this BiOCl/beta-FeOOH heterojunction exhibited superior visible-light response, fast photo-carrier migration, and high-efficient separation of photo-carriers, so that the BFOH-2 heterojunction possessed high-efficient hydrogen evolution reaction (HER) photocatalytic activity.