A photochemical simulation smog box, comprising a smog box body, a number of ventilation holes are arranged on the outer wall of the smog box body, a gas monitoring part composed of a plurality of monitoring probes is arranged on the smog box body, and a built-in light source is arranged in the smog box body Composed of the light source part, the smoke box is connected with a reaction gas distribution part for introducing gas and a power ventilation cleaning part for discharging gas in the box and introducing external air. The internal gas is blown from the top, right The gas is discharged from the screw-type ventilating hole. The gas is pressed in from the nitrogen dioxide gas distribution tank and hydrocarbon gas distribution tank on the left, and then guided into the box through the stainless steel conduit. The gas concentration in the box is determined by the on-line On-line monitoring records of monitoring probes; the invention adopts a disassembled design, which occupies a small area and is convenient to move. High, low power is safe and reliable, and the reaction cycle is short and the efficiency is high.