Low Density Parity Check（LDPC） code can reduce the signal error codes produced in fiber channel transmission and it can be used in the military fiber-optic communication system that has special requirements on accuracy and real-time performance of information transmission.In view of the performance demand of usual military fiber optic communication systems

the structure of LDPC code is analyzed.The quasi-below triangle check matrix strategy is applied to realize the encoding of LDPC code and the LLR-BP arithmetic is adopted for decoding.The encoder design is implemented in a chip of Field Programmable Gate Array（FPGA）.The results indicate that the design possesses much fine error correcting performance and can meet the demand of high accuracy and reliability for information transmissions of military fiber optic communication.