2,6-Bis(imino)pyridyl iron catalyst and traditional Ziegler-Natta catalyst were combined together as tandem catalytic system, activated with the mixture of TEA and MAO, and used for synthesis of branched polyethylene by in situ polymerization of ethylene. The branched polyethylene with branches from 8/1000C to 29/1000C was produced by adjusting reaction conditions: the amount of TEA, MAO, iron catalyst used, and reaction temperatures. Not only the short branches such as ethyl and butyl but also the longer branches (hexyl and longer than hexyl) were detected in the products. The products exhibited higher molecular weight and broader molecular weight distribution than those obtained from metallocene catalysts, which would provide the materials excellent mechanical properties and processability. (c) 2006 Wiley Periodicals, Inc.