The invention discloses a method for network scanning based on a trunk protocol, wherein the method comprises the following steps: 1) acquiring and analyzing configuration of a switch; 2) setting a test port to be in a trunk mode; 3) constructing and sending a test data packet; 4) receiving and filtering a response data packet; 5) restoring and processing data. The invention also relates to a system for network scanning based on the trunk protocol, wherein the system is specially used for the method, and comprises the following orderly connected modules: 1) a switch configuration acquisition and analysis module, 2) a module for setting the test port to be in the trunk mode, 3) a module for constructing and sending the test data packet, 4) a module for receiving and filtering the response data packet and 5) a module for restoring and processing data. With the method and the system provided by the invention, all VLAN or network segments on the switch can be switched one time, and configuration of the switch is not required to be modified, thus, network scanning efficiency is improved effectively, and influence of change of configuration of the switch on stable operation of an information system is avoided.