In this paper, a direct solar photocatalytic water splitting system with surface uniform concentrators (SUCs) is designed. Parameters influencing hydrogen production rates and energy conversion, viz. sacrificial agent concentration, catalyst concentration and circulation speed, are analyzed under typical days. It is found that the system with SUCs has better performances with higher sacrificial agent, higher catalyst concentration and lower speed: double and triple concentration of the sacrificial agent will improve the energy conversion efficiency by 4.52% and 19.35%, respectively; double and triple the photocatalyst concentration will improve the energy conversion efficiency by 81.32% and 200.00%, respectively; energy conversion efficiency under valve-half-closed and the valve-closed conditions are improve by 21.82% and 118.18% comparing with the valve-open condition. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.