In order to meet the needs of high-speed development of optical comm unication systems,a construction method of quasi-cyclic low-density parity-check (QC-LDPC) codes based on two different primitive elements of finite field is proposed.The Tanner graph of parity check matrix of the code constructed by this method has no cycles of length 4,which makes they have the excellent de coding convergence characteristics.Besides,by properly combining the two primitive elements of th e base matrix,the matrix structure is adjusted,so that the constructed code has a good distance property and an improvement of the error correction performance.Simulation results show that when the bit error rate (BER) is 10－6,in the same simulation environment,the net coding gain (NCG) of the proposed QC-LDPC(3780,3540) code with the code rate of 93.7% in this paper is improved 0.38dB than that of the PE-QC-LDPC(3780,3540) code based on the primitive element (PE) of finite field.In addition,the NCG of the proposed QC-LDPC(3780,3540) code is respectively 0.2dB and 0.72dB higher than those of the SG-QC-L DPC(3780,3540) code based on two different sub-groups (SG) over finite field,which is suitable for optical comm unication and the LDPC(32640,0592) code in ITU-T G.975.1w hich is widely used in optical communication.