The invention discloses a photocatalytic reactor. The photocatalytic reactor comprises a light source system, a reaction system, a sampling system and a control system and by the photocatalytic reactor, the functions of automatic and simultaneous sampling during the reaction process, synchronous reaction of multiple reactors, the control of reaction conditions and the like can be achieved. The photocatalytic reactor is characterized in that the light source of the light source system can be selected from ultraviolet light, visible light or natural light according to the experimental needs; the light source in the vertical direction produced by the light source system can be reflected by a light splitter and evenly divided into multiple horizontal lights to irradiate different reactors; the reaction system comprises multiple reactors which are same and mutually independent and is used for controlling the temperature of each reactor under the action of an external circulating fluid, each reactor is provided with a sampling switch and thus the manual sampling is achieved or the automatic sampling is achieved in combination with the sampling system. The device is simple in assembly and convenient to operate, the conditions of the photocatalytic reaction can be strictly controlled, the effects of different factors on the photocatalytic reaction are simultaneously explored and the photocatalytic reactor has application prospects in the field of photocatalytic researches.