The effects of initial beam distribution, divergence, energy divergence and geomagnetic field on the spatial transmission of particle beams were comprehensively analyzed, and the numerical modeling and quantitative numerical simulation of electrostatic diffusion and geomagnetic deflection effects were carried out. The simulation result shows that for particle beam with fixed beam energy and beam intensity, the electrostatic diffusion effect of the particle beam can be weakened by increasing the initial radius, and the exact direction of beam can be accurately predicted through accurate measurement of magnetic field. It can be seen that research on self-consistent force of charged particle beam and its interaction with external field is great significant to the study of generation, transport characteristics and engineering application of the particle beam.