Polymers have been widely used due to low cost, light weight, chemical inertness and easy of processing. However, bulk polymers are usually considered as thermal insulators owing to their low thermal conductivity. In this paper, the 3D polyethylene (PE) structure based on knitting method is proposed. We investigate the thermo-mechanical property of 3D PE and make a comparison with the amorphous PE. The results show that the 3D PE has a higher thermal conductivity, elastic modulus, and shear modulus than amorphous PE, which provides a novel perspective on designing high thermal conductivity polymers. In the past decades, although the strain effect on the thermal conductivity of PE has been intensively studied, little research has been focused on the impact of shear. In this work, the thermal conductivity of PE under different shear strain is calculated by molecular dynamics simulation. Unexpectedly, the impact of shear on the amorphous PE and 3D PE is different. For amorphous PE, the average thermal conductivity is insensitive to the shear strain. However, the thermal conductivity of 3D PE can be slightly enhanced when the shear strain is large enough. The underlying mechanism is related to the specific morphology. Our findings can deliver new insights on designing high thermal conductive polymers.