Abstract: In the disposal of nuclear waste, regulation and classification of transuranium elements, alpha radioactivity monitoring work in special places such as nuclear arsenal, we usually use the alpha energy spectrum measuring technique. Alpha energy spectrum measurement is one of the key measurements of nuclear radiation, which occupies an important position in the field of nuclear radiation monitoring. In order to accurately analyze the impact of different source-detector distance, vacuum degree, placement angle and other factors on alpha energy spectrum measurement, we used Monte Carlo method to simulate energy spectrum measurement, thus reduced experiment time and improved the accuracy. The Monte Carlo method was used to establish chamber model for the PIPS-alpha spectrometer, which, by changing the distance between a radiation source and detector, simulates the alpha energy spectrum. The simulation results are corrected according to the experimental results to improve the degree of agreement between experiment and simulation. Experiments show that the Monte Carlo model is accurate and can be used for simulating the impact of different source-detector-distance, vacuum degree, placement angle and other factors on alpha energy spectrum measurement. This method not can only be applied to other alpha energy spectrum measurement, but also be used in single energy spectrum research of alpha particles. The study is to provide a basis for the alpha spectrum measurement technology and data support for alpha spectrum technology.