The invention relates to a dust concentration abnormity monitoring devices, and aims to provide a system and a method for diagnosing filter bag damage by a laser radar. The system comprises a laser emission unit, a receiving and detection unit and a control and imaging unit; the laser emission unit comprises a counter, a laser driving circuit, a pulse laser and a collimating lens which are arranged in sequence; the receiving and detection unit comprises a lens cone, a reflecting mirror, a filter and a detector array which are arranged in sequence; the pulse laser, the laser driving circuit andthe counter are sequentially connected to the control and imaging unit through a signal line, and the detector array is connected to the control and imaging unit through a signal line; the control and imaging unit comprises a digital-to-analog signal converter and a computer. The system and method provided by the invention can be used for monitoring a bag dust removal cabin in real time, the phenomena of missing and false report of damaged filter bag are avoided, and the daily operation of a waste incineration power plant is not influenced at all. The system is simple to operate, the maintenance workload is small, the monitoring time is short, the feedback capability is strong, the efficiency is high, and missing detection is effectively avoided.