The concepts of combined switch, agent and multi-agent techniques are introduced. A type of new architecture of MAS is constructed. A monitoring and protecting solution of combined switch system based on multi-agent technique is proposed, the matrix algorithm is introduced to the identification and reconstruction of the system, and the function and methodology of every agent are introduced in detail. Under the condition of lab, voltage-regulator, relay-protection testing device and phase-shifter are used for simulating the actual situation of field, to fulfill the control-function test, protect-function test and running-without-fault test. From the test result, the solution proposed in this paper is available and reliable, and greatly improves the general-utility of the system software, truly realizes the random-combination function of the combined switch.