The invention refers to a method for a kind of double-gain multi-channel pulse amplitude analysis, which belongs to nuclear irradiation detecting field. The method amplifies the energy spectrum pulse signal to the low energy reference source and the measured source; carries on pulse peak broadening and peak position detecting to the two amplified energy spectrum pulse signal, when detects that the peak has passed by, starts the analog/digital transition and stores. The device includes photoelectric multiplier and linear amplifier, pulse peak stretcher, screening forming circuit, analog switch, analog/digital converter, data memory and peak detecting and forming circuit. The method uses additional low energy reference source, it doesn't affect the amplitude of the measured source, the measured source gamma ray spectrum generates an additional reference peak on the high address, thus the precision of the system can be upgraded. The invention stabilizes the peak of the additional reference peak, through adjusting the gain of the system, thus the peak of the measured source is stabilized.