Water crosslinking reactions of LDPE, PP, LLDPE, and the LDPE/PP and LDPE/LLDPE blends are investigated. Degrees of crosslinking of these samples are quantitatively compared and discussed in detail in terms of crosslinking ability, phase-separation behavior, molecular weight (or viscosity), morphology of the constituents in blends, or in the pure state. It is found that PP gives negligible crosslinking reactions in the pure state and in blends with LDPE. LDPE and LLDPE are both capable of giving considerable degrees of crosslinking, with LLDPE giving a higher degree of crosslinking than LDPE at all conditions studied. Degrees of crosslinking of the LDPE/ LLDPE blends are not linearly but are zigzagly related to the compositions of the blends with the LDPE/LLDPE = 50/50 blend giving a relatively high degree of crosslinking at 100, 120, and 140 degreesC for a certain time except the condition at 140 degreesC for 12 h compared with the LDPE/LLDPE = 75/25 and 25/75 blends.