Development of electronic devices, where the secondary electron emission is used to amplify input signals, requires simulation of complicated stochastic processes. The essence of the method proposed here consists of separating the amplification process into serial and parallel stages. The mean and variance of the amplitude distribution at the output of the entire system are obtained using the mean and variance of each stage. Theorems about serial amplification stages and parallel amplification paths constitute the key part of the method with partial Monte Carlo simulation for one simple stage. Here, the method is used to investigate the effect of the contact conducting layer on the gain and the noise factor of the channel amplifier. The case of image converters and intensifiers with an inverting electron-optical system and microchannel plate as an amplifier is taken for the consideration.