Abstract: The construction of low-density parity check codes with low encoding complexity and storage is a hot issue in the study of error correction coding. According to the existed research of QC-LDPC codes and eIRA codes, we propose a construction method for a kind of LDPC codes with enlarged dual diagonal structure, which fix eIRA codes as their base codes and take the advantages of low encoding complexity and storage. The construction of low-density parity check codes with low encoding complexity and storage is a hot issue in the study of error correction coding. According to the existed research of QC-LDPC codes and eIRA codes, we propose a construction method for a kind of LDPC codes with enlarged dual diagonal structure, which fix eIRA codes as their base codes and take the advantages of low encoding complexity and storage. In order to eliminate the influence caused by the import of degree-1 variable nodes during the extension of base matrix, we propose a joint degree optimization algorithm based on EXIT chart analysis. It improves the code performance significantly. Simulation results show that the code constructed in our method outperforms that in IEEE802.16e and IEEE802.11n standard about 0.1dB under same condition.