Abstract: Quantum cryptograph ensures the absolute security of key distribution on physics. However, not too high key transmission efficiency will be further reduced because of the noise in the quantum channel of key distribution. Having great flexibility with respect to block-length and rate, quantum Low Density Parity Check (LDPC) code based on sparse-graph becomes a hot topic in quantum error correction. Borrowing from the idea that the transmission reliability can be improved with error correction code in classical communications, a novel BB84 key distribution protocol is designed based on quantum LDPC in this paper. By numerical simulation, the effect of quantum error correction code on BB84 protocol is analyzed in the case of the transmission efficiency. The results show that quantum LDPC codes have good ability to overcome the noise, raise the transmission efficiency, and verify the availability of the proposed model.