Abstract: The solid state shear milling (S3M) followed by melt mixing process was applied to prepare Al/linear low-density polyethylene (LLDPE) composites with high performance. The effects of S3M pretreatment on the microstructure, crystallization, thermal stability, rheological behaviour, thermal conductivity and mechanical properties of the Al/LLDPE composites were systematically investigated. The results indicate the spherical Al particulates are squeezed into flakes during compounding with LLDPE by S3M, and their dispersion and interfacial adhesion are improved as well. Furthermore, the flaky Al with high radius-thickness ratio can be easier to form thermal network and orientation during processing especially at high filler loading. Consequently, the Al/LLDPE composites with S3M pretreatment show better crystallization and thermal properties, lower rheological percolation threshold, higher thermal conductivity and superior mechanical properties than Al/LLDPE composites prepared by conventional melt mixing. In particular, the rheological percolation phenomena of the composites with S3M pretreatment is observed around at 15% mass fraction of Al. When the mass fraction of Al is 80%, the thermal conductivity of Al/LLDPE composite with S3M pretreatment is as high as 8.86 W/(m·K), and its the tensile strength and flexural strength respectively are 33.0 MPa and 31.2 MPa, much higher than those of the untreated composite. And a significant increase of 13℃ in the onset temperature of degradation is also observed.