A system for effectively pre-distributing keys for a distributed sensor network is disclosed, The system includes: a plurality of sensor nodes, each of which has a sensing function, a calculation function, and a wireless communication function; and a base station which is connected to the sensor nodes over a wireless network, receives data from the sensor nodes, acts as a data central station, and distributes keys for inter-sensornode security authentication to the sensor nodes. A key management unit contained in the base station, generates a set of the sensor nodes used for security authentication between the sensor nodes, decomposes the set of the sensor nodes into a plurality of matrices, distributes the matrices to the sensor nodes, and allows the sensor nodes to search for a common private key required for the security authentication using the received matrices. Therefore, the system can always search for a common private key between the sensor nodes.