It is essential for wireless sensor networks (WSNs) to forward information collected by sensors to the sink quickly and efficiently through multi-hop relay. It is found that both duty cycle in the media access control (MAC) layer and the radio irregularity affect the efficiency of routing protocol greatly. Though traditional layered protocol has been proven to have the advantage of modularity, its whole performance cannot achieve its optimal performance since each layer works independently. Furthermore, most existing protocols that sacrifice time to improve energy-efficiency will bring unacceptable end-to-end delays to time-sensitive systems. This paper proposes a delay-constrained and energy-efficient cross-layer routing protocol (DECR), which takes into account related information of MAC and link layers when making routing decisions where the objective is to maximize the energy-efficiency of a node on the premise that end-to-end delay is restricted to the predefined upper bound. Both analysis and simulation results show that DECR performs well.