The invention discloses a pollution-free plastic degradation device. The device comprises a degradation machine body, wherein a cavity is formed in the degradation machine body, and a lighting and photo-thermal conversion mechanism is fixedly connected to the top end of the degradation machine body. The lighting and photo-thermal conversion mechanism comprises supporting rods, a hopper, a plane mirror, a material pipe, a rotating block, inserting openings, holding rods, a light gathering plate, fixing piles, an annular reflecting mirror, a water receiving barrel, a water supplementing pipe, acontaining plate, a water tank and a water pump. The plastic degradation device is scientific and reasonable in structure and safe and convenient to use, the lighting and photo-thermal conversion mechanism is arranged, sunlight is reflected to the plane mirror through the annular reflecting mirror in a 360-degree dead-corner-free mode, the sunlight is secondarily reflected through the plane mirror, thus, the sunlight is guided into the cavity to irradiate plastic in a degradation barrel, the plastic degradation efficiency is improved, and meanwhile, in the process of reflecting the sunlight, the sunlight is refracted through the light gathering plate, so that the sunlight is gathered, and the irradiation effect of the sunlight is improved.