Delay Tolerant Networks (DTN) is one of the mobile wireless networks that cannot set up the end-to-end communication path between the source and destination nodes pair in most of time. In this paper, we propose an improved routing protocol named as Dynamic Spray & Wait (DS&W), which is based on Spray and Wait routing strategy attempting to gain the higher delivery ratio benefits of replication-based routing as well as the lower resource utilization benefits of forwarding-based routing. But different from S&W, DS&W routing strategy focus on dynamic control to reduce the scale of the messages’ flooding by calculating the delivery success probabilities to destinations. DS&W routing protocol can dramatically reduce the overhead ratio in DTNs. Simulation results also evident that DS&W protocol outperforms other existing DTN routing protocols.