In a device for detecting and identifying a radioactive material, a coincidence device is configured to receive the first pulse signals and the second pulse signals from a first second detectors; a multi-channel analyzer is configured to receive the second pulse signals, count said second pulses and generate the energy spectrum of the gamma rays according to the counted second pulses, when the first pulse signals and the second pulse signals are both valid; a linear gate is configured to receive coincidence signals and being turned on, when the output signals of the coincidence device are valid, to allow the multi-channel analyzer to count the second pulses; and a determination device is configured to determine the type of the radioactive material emitting the gamma rays according to the generated energy spectrum and determine whether a radiation exists or not.