A Gamma count detector for radiation imaging pertains to the radiation detection art. The utility model comprises a detector component consisting of a photosensitive device and a flashing crystal, a circuit board which is connected with the detector component and includes an amplifying loop, a comparative loop and digital pulse output loop, a voltage regulator and a housing which accommodates the whole, on the end plane of the housing being provided an output socket which is connected with the circuit in the circuit board. The detector is characterized in that the flashing crystal, the surface of which is coated with a reflection layer or covered by reflective material, is coupled with the photosensitive device by optical glue. The integrated flashing crystal and photosensitive device is covered by the photophobic material and encapsulated in a metal box which is also covered by the photophobic material. Compared with the prior art, the utility model not only is more resistant to interferences, but also has smaller imaging dead arean on the plane of incidence, allowing for convenience in regulating the high voltage and upper/lower thresholds and connected with the followed-up circuit.