It cannot allocate reasonable bandwidth resources for power data under higher demand in real-time and for reliability in WSNs of a smart distribution grid. This is because the IEEE802.15.4 protocol adopts M/M/1/k queuing theory and the communication data follows the ‘first come first served’ principle. By setting rules of communication, the queuing problem is solved for different priority communication data in a node. A bandwidth resource prediction model of multi priority data is established, where communication delay and BER are taken as a constraint condition and maximizing the utilization of network bandwidth is the objective function of the system. From the bandwidth prediction results, the communication network allocates the data bandwidth resources for different priority data at the next time. Finally, a case is tested, based on 40-node of WSNs applied in a smart distribution grid to verify the effectiveness of the proposed allocation scheme. This work is supported by the National Natural Science Foundation of China (No. 51877060).