To address the issues of poor storage stability and low-temperature crack resistance in waste plastic-modified asphalt， a twin-screw extruder was employed to pretreat waste polyethylene （PE） and subsequently it was combined with bio-oil to produce bio-oil/pretreated waste PE composite modified asphalt. Storage stability， low-temperature crack resistance， and high-temperature stability of modified asphalt were examined by separation test， rheological property test， fluorescence microscopy test， and Fourier-transform infrared spectroscopy test. The results show that the density of the pretreated waste PE is close to that of asphalt， and the presence of more polar groups and C=C structures increase its chemical activity， significantly enhancing the storage stability of waste PE modified asphalt. The bio-oil/pretreated waste PE composite modified asphalt forms a continuous network structure， which further improves the storage stability of waste PE modified asphalt and significantly increases its low-temperature crack resistance， while reduces its high-temperature stability.