A method for amplitude digitization of a nuclear pulse, comprising steps of: applying, by a constant fraction discrimination timing circuit, a CFD timing process on a subject pulse signal output from a nuclear event energy detector, and outputting a CFD timing signal for indicating an arrival time Td of a present nuclear event; applying, by a shaping circuit, a shaping process on the subject pulse signal to obtain a subject shaped signal with amplitude Vot; characterized in the further steps of: comparing, from a time To, values taken at the same time from the subject shaped signal and a dynamic threshold signal, and taking, as an over-threshold time Tot for the present nuclear event, a time when the value of the dynamic threshold signal changes from less than the value of the subject shaped signal to not less than the value of the subject shaped signal, wherein a time length between Td and To is preset as ΔT; wherein the following equation holds: Tot − To Vot = Tot 2 − To Vot 2 = Tot 1 − To Vot 1, wherein Tot1 represents an over-threshold time for a first shaped signal when compared with the dynamic threshold signal, Vot1 represents an amplitude of the first shaped signal, Tot2 represents an over-threshold time for a second shaped signal when compared with the dynamic threshold signal, Vot2 represents an amplitude of the second shaped signal, such that the amplitude Vot of the subject shaped signal is linearly proportional to Tot-Td+ΔT or to Tot-Td-ΔT; and wherein a digital quantity representing a result of digitalization of an amplitude Vot of the subject shaped signal, is determined by converting a time length between Td and Tot. applying, by a constant fraction discrimination timing circuit, a CFD timing process on a subject pulse signal output from a nuclear event energy detector, and outputting a CFD timing signal for indicating an arrival time Td of a present nuclear event; applying, by a shaping circuit, a shaping process on the subject pulse signal to obtain a subject shaped signal with amplitude Vot; characterized in the further steps of: comparing, from a time To, values taken at the same time from the subject shaped signal and a dynamic threshold signal, and taking, as an over-threshold time Tot for the present nuclear event, a time when the value of the dynamic threshold signal changes from less than the value of the subject shaped signal to not less than the value of the subject shaped signal, wherein a time length between Td and To is preset as ΔT; wherein the following equation holds: Tot − To Vot = Tot 2 − To Vot 2 = Tot 1 − To Vot 1, wherein Tot1 represents an over-threshold time for a first shaped signal when compared with the dynamic threshold signal, Vot1 represents an amplitude of the first shaped signal, Tot2 represents an over-threshold time for a second shaped signal when compared with the dynamic threshold signal, Vot2 represents an amplitude of the second shaped signal, such that the amplitude Vot of the subject shaped signal is linearly proportional to Tot-Td+ΔT or to Tot-Td-ΔT; and wherein a digital quantity representing a result of digitalization of an amplitude Vot of the subject shaped signal, is determined by converting a time length between Td and Tot. comparing, from a time To, values taken at the same time from the subject shaped signal and a dynamic threshold signal, and taking, as an over-threshold time Tot for the present nuclear event, a time when the value of the dynamic threshold signal changes from less than the value of the subject shaped signal to not less than the value of the subject shaped signal, wherein a time length between Td and To is preset as ΔT; wherein the following equation holds: Tot − To Vot = Tot 2 − To Vot 2 = Tot 1 − To Vot 1, wherein Tot1 represents an over-threshold time for a first shaped signal when compared with the dynamic threshold signal, Vot1 represents an amplitude of the first shaped signal, Tot2 represents an over-threshold time for a second shaped signal when compared with the dynamic threshold signal, Vot2 represents an amplitude of the second shaped signal, such that the amplitude Vot of the subject shaped signal is linearly proportional to Tot-Td+ΔT or to Tot-Td-ΔT; and wherein a digital quantity representing a result of digitalization of an amplitude Vot of the subject shaped signal, is determined by converting a time length between Td and Tot. wherein Tot1 represents an over-threshold time for a first shaped signal when compared with the dynamic threshold signal, Vot1 represents an amplitude of the first shaped signal, Tot2 represents an over-threshold time for a second shaped signal when compared with the dynamic threshold signal, Vot2 represents an amplitude of the second shaped signal, such that the amplitude Vot of the subject shaped signal is linearly proportional to Tot-Td+ΔT or to Tot-Td-ΔT; and wherein a digital quantity representing a result of digitalization of an amplitude Vot of the subject shaped signal, is determined by converting a time length between Td and Tot.