Comparing with binary low-density parity-check (LDPC) codes, non-binary codes really have some advantages, but its high complexity decoding is a big challenge for implementation. For resolving the problem, the proportional logic truncation mechanism algorithm based on iterative soft-reliability is proposed because the algorithm only involves finite field addition, multiplication and integer operations, and it can divide variable nodes into processing and non-processing nodes. Only some of the variable nodes participate in the actual information processing in the iterative process, so the algorithm has lower decoding complexity than other algorithms. Comparing with ISRB, IISRB and RS-IISRB algorithms through simulation experiments, the proposed algorithm has better performance. It has widely application in radio and optical communication for its good error-correcting performance and low complexity.