We propose a four-state reference-frame-independent quantum key distribution (RFI-QKD) protocol with the heralded pair-coherent source (HPCS). We investigate the performance of the proposed protocol and simulation results show that our protocol can achieve a high key generation rate in long-distance transmission, taking source flaws and statistical fluctuations into consideration. Although fewer states are used, this protocol not only has a higher key generation rate at the same transmission distance but also a longer transmission distance with the same secure communication compared with the original six-state RFI-QKD protocol using the weak coherent source (WCS).