A passive optical network (PON) is an auspicious access technology that keeps track of emerging application diversity. When it comes to the point of handling multiple service types together in the same network with resource limitation, there comes the important term of prioritization as all of the services do not need the same quality of service. In this paper, an efficient resource allocation scheme based on service prioritization is proposed for 100 Gb/s next-generation Ethernet passive optical network (NG-EPON) upstream. Higher-priority service quality is ensured despite load fluctuation. The proposed prioritization scheme by accessing the multiple wavelengths for higher-priority service classes also enhances bandwidth utilization. Higher-priority classes can work suitably using excess bandwidth occupied by the low-priority services during increasing demand. Further increment can preempt low-priority bandwidth for higher-priority services. We performed extensive simulation and got that at 11 % overloaded network case, the highest priority service delay of 379 msec decreased to 5 msec from the non-priority scheme to the priority scheme. The jitter of 1.06 μsec decreased to 0.035 μsec. This prioritization does not decrease the bandwidth utilization which was found near 99.26 % excluding the overhead. The proposed scheme achieves stable performance of the higher-priority service classes.