The influence of hot water and the water-carrying agent aluminum potassium sulfate dodecahydrate (alum) on the mechanical and thermal properties of the silane-water crass-linked linear low density polyethylene (LLDPE) was investigated. LLDPE was melt-grafted with various content of vinyl trimethoxysilane (VTMS) using dicumyl peroxide (DCP) as initiator. The results show that the contribution of hot water to gel content is poor, about 2 to 16%, compared with that of the silane grafted LLDPE. Is feasible to achieve silane-water crosslinking reaction with alum for self-crosslinked LLDPE; furthermore, the self-crosslinked LLDPE has lower crosslink density (v). It was found that alum could not only conduct silane-water crosslinking reaction effectively, but also improve the mechanical properties, especially the elongation behavior. The heat of fusion (Delta HM), the melting temperature (Tin), and the degree of crystallinity (Xc) of the hot water crosslinked LLDPE decreased with the advancement of VTMS. The Avrami exponent n of self-crosslinked sample was larger than that of hot water crosslinked sample. This means that the alum could contribute to the growth of crystallization.