The problem of white pollution caused by waste agricultural mulch film (WAMF) has a long history and has brought great damage to the soil and ecological environment. The recycled WAMF has no processing performance because it is doped with a large amount of cotton straw and soil inorganic particles. In this study, it was reported for the first time that high‐quality and efficient recovery of WAMF was carried out by means of solid‐state shear milling (S3M) technology. After the pretreatment of S3M, the recycled WAMF is transformed into an active composite powder with a particle size of microns, which regains certain processing performance. Then we prepared a composite material similar to WPC (wood‐plastic composite) by using the composite powder. It was found that under the action of strong three‐dimensional shear force, the phase domain size of the composite decreased significantly, and the compatibility of each component improved. The macroscopic performance was that the tensile strength was increased by 65% and the bending strength was increased by 74%, reaching 8.30 and 17 MPa, respectively. The 24‐h water absorption of this composite decreased by 13%. More importantly, the thermal stability was not significantly reduced during the milling process. This process does not require sorting, cleaning, or other operations, which can greatly simplify the process flow and improve recovery efficiency. It provides an effective solution to the problem of white pollution caused by WAMF. Preparation of WPC/SIP composite by S3M technology and the effect of milling times on the mechanical properties of composites.