Long chain branching LLDPE was prepared via initiating the long chain branching reaction of matrix LLDPE by preirradiated LLDPE. The effects of irradiation dose,rLLDPE content on the long chain branching reaction were studied. The long chain branching LLDPE was characterized by MFR test,GPC,13C NMR and torque test. The results show that:compared with matrix LLDPE,the MFR and processing torque of long chain branching LLDPE decrease,the MFR ratio (M10/M2) increases obviously; the optimum irradiation dose is 15kGy,and the optimum rLLDPE content is 50% for long chain branching reaction; the long chain branching amount is up to 1.4/10 000C determined by 13C NMR.