The main drawback of all current theories of scintillation spectrometers is in introducing various terms into the formula for the energy resolution of scintillation spectrometers, without giving specific formulae for the relationship of these terms with characteristics of scintillation detectors. Such insertion of various contributions by “hands” is not only wrong but also counterproductive, since it does not allow comparing the results obtained by different scientific groups. In this work, the microscopic mathematical model was formulated, which serves as the basis for the standard theory of scintillation spectrometers. The standard theory allows obtaining the formulae for arbitrary moments of the signal distribution function at the output of the scintillation spectrometer. In particular, the formulae for the average value and the variance of the signal at the output of the photodetector are obtained. The structure of the formula for the energy resolution of a scintillation spectrometer reveals the contributions of the processes that take place at converting the energy of a primary particle into the output signal, particularly the contribution associated with the nonlinearity of the scintillator light output. It was shown that in the developed standard theory of scintillation spectrometers there are no drawbacks of the currently existing theories of scintillation spectrometers. Thus, the developed standard theory of scintillation spectrometers creates a solid basis for linking theoretical and experimental researches in this field.