Abstract: By analyzing the degree distribution of low density parity check (LDPC) codes in definite quantity with gaussian approximation (GA) and optimal method, the performance of degree distribution for LDPC codes is investigated. Research results show that when the initial channel state and degree distribution of the LDPC codes are known, the optimal retransmission fractions can be determined. Maximum retransmission efficiency would be achieved if bits can be retransmitted according to these fractions. Calculation results reveal that the retransmission fractions in degree distribution based hybrid automatic repeat quest (DDB-HARQ) scheme are optimal.