  The generation of the population oscillation of the multicomponent spinor
Bose-Einstein condensate is demonstrated in this paper. We observe and examine
the nonsynchronous decreasing processes of the magnetic fields generated
between quadrupole coils and Ioffe coils during the switch-off of the
quadrupole-Ioffe-configuration trap, which is considered to induce a
nonadiabatic transition. Starting from the two-level Schr\"{o}dinger equation,
we have done some numerical fitting and derived an analytical expression
identical to the results of E. Majorana and C. Zener, of which both the results
well match the experimental data.
