Abstract: This paper uses Bayesian inference to compare the global main magnetic field models, and compares the model order of data preference based on Bayesian evidence. It provides a statistical basis for the order selection of the main magnetic field.Using the Swarm satellite data, Using the Swarm satellite magnetometry data, we estimate the evidence for different orders of the main magnetic field model.The results show that in the order of the main magnetic field from 0 to 20, order N=12 has the global best evidence. Referring to the threshold interval given by Jefrrey's scale, the data preference for order N=12 is significantly better than other orders.the results match the power spectrum analysis of the 14th order spherical harmonics.