The invention discloses a phytotron haze environment simulating device and a haze environment simulating method thereof. The device comprises a phytotron, a haze parameter detection unit, a cloud mist generation unit and a dust-haze generation unit, the haze parameter detection unit is arranged in the phytotron, and the output end of the cloud mist generation unit and the output end of the dust-haze generation unit are communicated with the interior of the phytotron. The simulating method comprises the steps that dust-haze particle raw materials are prepared and evenly mixed, the clout mist generation unit is started to form a cloud mist environment, the dust-haze generation unit is started to form a dust-haze environment, and mutual superposition, chemical combination and even mixing of mist steam and dust-haze particles are facilitated to form a haze environment. According to the phytotron haze environment simulating device and the haze environment simulating method thereof, PM2.5 particles and the stable haze environment of which the cloud mist concentration, chemical components of dust-haze particles and particle size distribution can be freely controlled and adjusted can be formed in the phytotron, and a safe and reliable experiment support is provided for researching the influence of the haze environment on human body health, outdoor traffic and electrical external insulation equipment.