A quantum key distribution scheme based on heralded single photon sources and quantum memory is studied. The relationship between key generation rate and safe transmission distance and storage time is analyzed, and the effect of decoherence effect of quantum memory on the final key generation rate is analyzed. The influence of quantum memory on measurement-device-independent quantum key distribution scheme based on heralded single photon sources is studied. The simulation results show that under heralded single photon sources, the increase of the actual coherence time of the quantum memory makes the safe transmission distance of the system increase, and the quantum decoherence effect has a weak influence on the final key generation rate.