The decoding complexity is the main issue in designing DVB-S2 Low Density Parity Check (LDPC) decoder. This paper proposes a low complexity decoder, which is based on a new row message passing Offset Min-Sum algorithm. The proposed algorithm can reduce the complexity of the decoder with no performance loss. The simplified node update units based on the proposed algorithm and the memory organization optimized across different code rates play the key role in reducing the complexity. The synthesized area of the decoder is 9.6 mm² in Chartered 90 nm COMS technology. When the code rate is 9/10 and the work frequency is 320 MHz, the net throughput of the decoder is 998 Mbps.