IEEE 802.15.4 standard defines the physical layer and medium access control layer protocols for low-rate wireless personal area networks (LR-WPANs). In IEEE 802.15.4 LR-WPANs, quality-of-service is supported by using the guaranteed time slots (GTS) to transmit real-time packets since a LR-WPAN device doesn't need to contend the channel in the GTS. In the PAN coordinator, requests of GTS are allocated based on the first-come-first-service policy. However, with the increasing of multimedia applications, this original design has suffered from the lack of priority mechanism to support the transmission of real-time packets. In this paper, we propose a non-preemptive priority-based polling scheme for the GTS allocation in IEEE 802.15.4 LR-WPANs. The proposed scheme can ensure that the connections which have higher priority can transmit real-time packets quicker. The simulations show that the proposed scheme can achieve more GTS allocations, higher throughput, better bandwidth utilization and lower packets access delay time.