Abstract: The AE-8/AP-8 models, which were constructed by NASA with satellite obser-vation data in the 1960s and 1970s, have long been considered to be the standardtrapped radiation models. It seems that they will continuously be used for a certainperiod of time in the future. The weakening of the geomagnetic field causes the driftshell of a charged particle to descend and the structure of the Trapped RadiationBelt to deform. Thus it is of importance to correctly use the AE-8/AP-8 models inthe contemporary era. However, up to now there seems to be no consensus on thisissue- On the basis of physical analysis, we propose the Drift Shell Tracing Method(DSTM) in this paper to solve the problem. The DSTM provides a reasonable wayto apply the standard trapped radiation models within the adiabatic approximation. The calculation results indicate that the change of the geomagnetic field playsa significant role in the particle redistribution in the inner zone. It is found that inthe past three decades,the central location of the particle South Atlantic Anomaly(SAA) has drifted westward almost 20° in longitude and northward almost 1Oo inlatitude. In the altitudes of 300-400 kilometers, the intensity of proton flaxes hasvaried dramatically and the flux difference at the same location can even be up to3-4 orders of magnit1lde.