A different representation of recur-sive systematic convolutional (RSC) codes is pro-posed. This representation can be realized by a con-ventional Tanner graph. The graph becomes a treeby introducing hidden edge. It is shown that thesum-product algorithm applied to this graph modelis equivalent to the BCJR algorithm for turbo de-coding with lower computational complexity. Themessage-passing chain of the BCJR algorithm is pre-sented more exactly in the graph. In addition, theproposed representation of RSC codes provides an ef-ficient method to set up the trellis and the conven-tional Tanner graph for RSC codes provides directlythe architecture for decoding.