A test method and system for PLC security defense device are provided. The method including: acquiring by the first test end the information about the device under test, involving the type of communication mode, the type of PLC, the attack type and/or attack rule; after the attack messages to the device under test being generated and sent to the device under test, obtaining by the first test end the assessment results of the PLC security defense device on the basis of the second test end's response message. This is a fast, objective and thorough assessment method to testify security defense function of the device under test.