Hydrogen production by photocatalytic water splitting (HPPCWS) is a promising clean energy conversion technology. However, this technology lacks quantitative environmental impact information and comparison with other hydrogen production technologies. In the process of the technology scale-up, the environmental impact assessment of the whole life cycle is essential. Life cycle assessment (LCA) based on a pilot plant of HPPCWS constructed in China is conducted to evaluate the environmental performance using Simapro software. As the source of inventory, the continuous hydrogen production characteristics of the system are predicted by using local radiation data and reveal that the cumulative hydrogen production of the system is closely related to the local radiation data and the time intervals for replacing the reaction solution. The LCA results on environmental impact show that the construction stage of the system has a more significant impact. In contrast, the dismantling stage can offset part of the environmental impact due to partially recycling primary materials. Transportation and power consumption are the main factors affecting the environment during system operation. The value of the leading midpoint indicator, global warming potential (GWP), could be as low as 4.53 kg CO₂ eq/kg H₂ under suitable design conditions. Compared to other hydrogen production routes, this work has significant advantages on environmental impact, while there is no denying that the application of the system is facing opportunities and challenges. The results reflect the problems that should be paid attention to in the process of the technology scale-up from the aspects of material and energy utilization and environmental risk. This paper aims to provide credible data on the environmental impact of photocatalytic hydrogen production technology and supply a professional reference for industry decision-making on complete process control.