A long-lasting light conversion film and a preparation method therefor. The light conversion film comprises a first protective layer, a light conversion layer arranged on the first protective layer, and a second protective layer arranged on the light conversion layer. The protective layers consist of at least one plastic layer and at least one isolation layer. The preparation method for the light conversion film is as follows: 1) respectively preparing a plastic layer premix and an isolation layer premix; 2) uniformly mixing a matrix resin, a light conversion agent, a lubricant, a light stabiliser and an antioxidant to obtain a light conversion layer premix; 3) adding the plastic layer premix, the isolation layer premix and the light conversion layer premix to a co-extruder, and performing multi-layer co-extrusion. The isolation layer in the light conversion film effectively blocks moisture and oxygen in the air, and prevents the light conversion agent in the light conversion layer from coming into contact with moisture and oxygen and breaking down, thereby increasing the stability of the light conversion agent, and significantly extending the service life of the light conversion film.