Based on the genetic algorithm (GA), a new genetic probability decoding (GPD) scheme for forward error correction (FEC) codes in optical transmission systems is proposed. The GPD scheme can further offset the quantification error of the hard decision by making use of the channel interference probability and statistics information to restore the maximal likelihood transmission code word. The theoretical performance analysis and the simulation result show that the proposed GPD scheme has the advantages of lower decoding complexity, faster decoding speed and better decoding correction-error performance. Therefore, the proposed GPD algorithm is a better practical decoding algorithm.