The purpose of this research is to modify the elongational flow behavior of polycarbonate (PC). PC is one of the engineering polymer which has outstanding mechanical, optical, electrical and thermal properties. PC is linear polymer and an improvement of the melt strength of PC is required in some applications. We modified melt-polymerized PC by incorporating reactive agent (chain extender). The modification enhanced storage modulus G' as increasing content of the chain extender, while the loss modulus G" did not show such significant change. The modified PC did not exhibit thermorheological simplicity. Furthermore, the modified PC showed noticeable increase of the stress under elongational flow which is never expected for standard PC.