The invention relates to a method for testing a network device, which comprises the steps: setting Port-number, PVID and VLAN of each port on a reference switch, connecting a first port of the reference switch with a package generating device, generating a plurality of packages and transferring the packages to the first port by the package generating device, copying the packages after receiving the packages by the first port, transferring the packages to a second port and a third port corresponding to other PVIDs in the VLAN belonging to the first port so as to generate a package storm loop, setting a fourth port, a fifth port and VLANs thereof so as to receive the packages from the second port and the third port, connecting the fourth port and the fifth port with two ports on a switch tobe tested so as to form a package transfer loop, modifying the PVIDs of the fourth port and the fifth port and the VLAN of the first port so that the packages transferred to the first port can be directly copied and transferred to the fourth port and the fifth port, stopping the generation and the transfer of the packages, and transferring the speed and the quantity of the packages back by the switch to be tested to judge the efficiency of the packages.