A system for operation and maintenance of network devices, including a device layer including at least one network device and a pre-processing layer including pre-processing device(s); the network device obtains a CDR of a call and transmits the CDR to the pre-processing device; the pre-processing device filters the CDR and performs centralized operation and maintenance of network devices. The network device forming the device layer, the pre-processing device forming the pre-processing layer and a method for operation and maintenance of network devices in the above system are also provided. Through the technical scheme, call services are separated from operation and maintenance management and functions of the network devices are unified, which results in more stable operation of the network devices; the operation and maintenance management will be more flexible and it becomes easier to monitor the whole network and to perform operation and maintenance of network devices.