Diagnostic system and method for diagnosing system in open-cable set-top box system

PURPOSE: An open cable set top box diagnosing system and the method thereof are provided to previously diagnose the operation status of a set top through a POD(Point Of Deployment) module by adding a diagnosis resource to a resource defined for POD interface. CONSTITUTION: The operation status of the set top is checked through a security module of a cable head-end by adding a diagnosing resource which can check the operation status of the set top to a resource layer defined for the interface between the security module and the set top in an open cable set top box in which the security module and the set top are separated. Set top manufacturing makers are connected to the cable head-end through a network for enabling the bidirectional telecommunication to the cable head-end. The cable head-end periodically checks the operation status of the set top through the security module, and informs the diagnosis information of a set top having a problem of the corresponding set top manufacturing makers through the network in real time.