Quantum key distribution (QKD) is an absolutely secure key distribution guaranteed by quantum physics and has attracted significant attention. Among existing quantum key distribution protocols, the round-robin differential phase shift quantum key distribution protocol (RRDPS-QKD) has significant advantages in practical applications because of its large error tolerance. In this study, a novel round-robin differential phase shift quantum key distribution protocol is proposed. The received pulse trains are divided into odd and even branches using a switch. A random delay device, followed by a delay device, are added to each branch so that all the pulses from the source can participate in the interference at the receiver, and thus, improve the utilization rate of the pulse trains. The proposed protocol also ensures that the source can transmit the pulse trains continuously. The simulation analysis results and simulation quantum key distribution experimental results show that the proposed protocol can considerably increase the interference probability of the pulse trains and effectively improve the security key rate of the round-robin differential phase shift quantum key distribution protocol.