In this paper, based on the background of hydrogen photolysis of water, adapts the computational fluid dynamics software combined with secondary development to numerically analyze the heat transfer process inside the solar photocatalytic reactor. A high⁃quality structured hexahedral photocatalytic reactor grid was established to analyze the temperature distribution characteristics of the solar photocatalytic reactor model numerically, compile the Gaussian heat flow and validate the model combined with the solar photocatalytic water activity evaluation system for hydrogen production. This article will focus on the effect of solar radiation on the temperature distribution of the fluid inside the reactor and the reactor under full spectrum, and study the differences in temperature distribution and causes under different conditions.