Crosslinking modification is one of the important methods of polyethylene modification. The effects of crosslinking degree and resin structure on rheological properties, crosslinking properties, crystallization properties and mechanical properties of crosslinked high density polyethylene (XHDPE) were studied. The results show that when the mass fraction of crosslinking agent increases from 0 to 1.2%, the maximum energy storage modulus (G'_max) and gel content of XHDPE increase, and the minimum value of loss factor (tanδ _min) decreases gradually. With the increase of the content of crosslinking agent, the crystallinity and grain size of XHDPE decreases, and the crystallization capacity decreases. After the addition of crosslinking agent, the tensile yield strength of XHDPE decreases gradually, the elongation at break increases first and then decreases, and the impact strength increases significantly. With the same content of crosslinking agent, the energy storage modulus of XHDPE and the viscoelasticity of macromolecular network increase gradually with the increase of molecular weight of base resin. When the elongation at break of high molecular weight HDPE reaches the maximum, the content of crosslinking agent required is lower. High molecular weight HDPE base resin is beneficial to improve the mechanical properties of crosslinked samples.