The invention discloses a multifunctional photocatalytic reaction device, which consists of a gas circulation system, a photoreaction system, a separation system, a detection system and a light source system. The light source can be ultraviolet light, visible light and sunlight and is arranged outside a quartz reactor, light penetrates through the quartz reactor to excite a photocatalyst in order to initiate photocatalytic reaction, the photocatalyst can be a thin film which is immobilized, together with a carrier, inside the reactor, or be particles suspended in reaction liquid. The reactor is suitable for liquid-solid, gas-solid and gas-liquid-solid phase photocatalytic reaction, favoring the research on photocatalytic reaction dynamics. The multifunctional photocatalytic reaction device of the invention is suitable not only for photocatalytic reduction CO2 reaction, but also for the fields such as photocatalytic degradation of organic pollutants, hydrogen production by water photolysis, photochemical synthesis and the like, besides, both intermittent operation and continuous operation can be implemented, and inert gas protection can be performed in the reaction process.