1. A network switching system for processing packet switching, comprising: a first memory, for storing a first packet among a plurality of packets; a second memory, for storing a second packet among the plurality of packets; a memory selecting unit, for selecting the first memory or the second memory for storing each of the plurality of packets according to whether a traffic of the network switching system is congested; a buffer manager, for managing the first memory and the second memory; a queue manager, for managing a plurality of queues of a plurality of network ports; and a forwarding engine, for obtaining a destination queue of a destination network port among the plurality of network ports for each of the plurality of packets; wherein attributes of the first memory and the second memory are different.