In this paper,the expandable graphite was used as raw material,and the graphene /HDPE composites were successfully prepared by microwave heating and melt blending.The properties were characterized by scanning electron microscopy(SEM),differential scanning calorimetry(DSC),X-ray diffractometry(XRD)and tensile test.The results show that thick graphene(TSG)has good compatibility with HDPE matrix.At the same time,graphene with lamellar structure provides heterogeneous nucleating agent for HDPE crystallization,which improves its crystallinity.When the mass fraction of TSG content was 0.3%,the HDPE tensile strength increased from 22.5 MPa to 24.9 MPa,increased by 10.5%,the bending modulus increased from 443.5 MPa to 510.4 MPa,increased by 15.1%,and the impact strength increased from 55.3 kJ/m² to 56.0 kJ/m²,increased by 1.3%.The mechanical properties of the composites are obviously improved.