基于修饰技术提出了一种改进的准循环低密度奇偶校验(QC-LDPC)码的构造方法。该方法构造的QC-LDPC码具有较低的编码复杂度，其校验矩阵围长至少为6，避免了四环的出现，具有良好的围长特性。仿真分析表明： 通过该构造方法构造的码率为93.7%的QC-LDPC(3969,3717)码在降低其编码复杂度的情况下，拥有与其对应的未应用修饰技术的QC-LDPC（3969,3719）码相媲美的纠错性能；并且在相同条件下，QC-LDPC(3969,3717)码的纠错性能要好于利用随机构造方法构造的PEG-LDPC(3969,3720)码，以及ITU-T G.975中已广泛用于光通信系统中的RS(255,239)码和LDPC(32640,30592)码，更适合于光通信系统。

An improved construction method of quasi-cyclic low-density parity-check(QC-LDPC) codes, based on the making technology is presented. The QC-LDPC codes constructed by this improved construction method have lower encoding complexity, and their parity-check matrices can effectively avoid the girth-4 phenomena and have the advantages such as better girth-length properties and more flexible adjustment in the code-length code-rate. The simulation results show that the error-correction performance of the QC-LDPC(3969,3717) with the code-rate of 93.7% constructed by this improved construction method is as good as the error-correction performance of the QC-LDPC(3969,3719) code which is constructed without the making technology. Furthermore, at the same simulation conditions, the error-correction performance of the QC-LDPC(3969,3717) is better than that of the PEG-LDPC(3969,3720) code constructed by the random construction method, the classic RS(255,239) code which is widely used in optical communication systems and the LDPC(32640,30592) code in ITU-T G.975.1. Therefore, it is more suitable for optical communication systems.