The present invention provides a method for stream testing by a switching hub including the steps of generation a test data stream by the switching hub and testing a plurality of DUTs by using the test data stream. A first port of the switching hub transmits port mirroring to a second port of the switching hub. A packet is transmitted through a physical cable from the first port. The first port and the second port are added to a first virtual local area (VLAN) in a native manner. The second port receives a test packet in a self-loop mode. The test data stream is created by repeatedly transmitting the test packet from the second port. In addition, the present invention further provides a system for stream testing by a switching hub.