The paper introduces the frame principle of a portable natural gamma spectrum. In order to realize spec-trum stabilization

a scaled related curve of temperature and negative high voltage of photo-multiplier-tube (PMT) is used to control negative high voltage of PMT to get stable gain of the instrument system and to realize rough adjust-ing of spectrum stabilization. Then the energy axis of gathered data curve is re-demarcated by using positions of natu-ral gamma radial characteristic peaks to obtain gamma spectra form the curves of pulse-amplitude-count-rate without the process of refine stabilizing spectra in the similar instruments. So

the method in this paper can greatly improve the speed of data acquisition on the same condition of error due to statistical.