A round-robin differential phase shift quantum key distribution (RRDPS-QKD) protocol based on heralded pair-coherent source (HPCS) and orbital angular momentum is proposed. The superposition state consisting of multiple orbital angular momentum states with different topological charges is used as the information carriers to remarkably increase the key generation rate. HPCS is used as the quantum source to decrease the ratio of vacuum and multi-photon pulses and to dramatically increase the key generation rate. Moreover, the propagation characteristics in the turbulent atmosphere channel are analyzed, and the influence of both channel attenuation and atmospheric turbulence on the protocol is considered.