In order to analyze the dynamic characteristics of a general-purpose machine gun when shooting in different soils and improve its shooting accuracy, a certain type general-purpose machine gun is taken as the research object, a 3D model is established in SolidWorks, and its coupling model in different soils is established through ABAQUS software. It conducts computational modal analysis, establishes an experimental system and performs excitation, parameter measurement and analysis on the machine gun to obtain its experimental modal parameters. Theoretical and experimental results show that the model has high accuracy and has certain guiding significance for understanding the dynamic characteristics of the mechanism and the structure design of the machine gun frame.