The cross-linking reaction of polyethylene/peroxide system was studied at elevated temperature. The dynamic modulus evolution was monitored within linear viscoelastic regime by parallel plate rheometer. Different strains were chosen to represent different flow fields. Based on the mechanism of cross-linking reaction, a new expression relating recombination rate constant with rheological conversion was derived. The experimental and calculated results showed that the strain had substantial effects on the cross-linking reaction kinetics. Consequently a formula reflecting the effect of the complex viscosity on recombination rate constant was found, which was further integrated into the classical Arrhenius kinetic equation. (c) 2005 Society of Plastics Engineers.