Abstract: A gate radiation monitoring system and method for instant gamma analysis on passing by objects is related to two photomultiplier tubes respectively installed at the two ends of the column plastic scintillation detectors. By use of precise high frequency clock with period about 10 nsec, the analog pulse signals from the all photomultiplier tubes which respond the ionizing gamma events of the plastic scintillation detectors can be converted into logic signals by the discrimination circuit. The continuous timing records can be built in sync. for all PMTs by personal computer. It has been proved that through the present invention, conventional gate detector can be applied to quick determination of the surface radiation intensity, the energy and location of the gamma emitters contained in the detected objects.