In this paper, we propose and analyze a new relaying scheme for the three-node cooperative system, named as clustering-based relay selective decode-and-forward (CSDF). The source broadcasts a parallel concatenated recursive systematic convolutional (RSC) code to both the relay and the destination. When the decoding error is detected at the relay, a kernel K-Means clustering algorithm is applied to distinguish the reliable bits from the unreliable bits. The relay then forwards the bits that are deemed reliable and discards the bits that are not, resulting in less errors propagating to the destination. The closed-form expression of bit error rate(BER) is derived to demonstrate the relation between error propagation and system performance of our proposed relaying scheme. Simulation results show that the proposed scheme achieves better performance and efficiently reduce error propagation.