- Abstract The pickup ion dynamics and mechanism of multiple reflection and acceleration at the structured quasi-perpendicular supercritical shock are studied. The motion of the pickup ions in the shock is studied analytically and numerically using the test particle analysis in the model shock front. The analysis shows that slow pickup ions may be accelerated at the shock ramp to high energies. The maximum ion energy is determined by the fine structure of the electromagnetic field at the shock ramp and decreases when the angle between the magnetic field and the shock normal decreases. Evolution of pickup ion distribution across the nearly perpendicular shock and pickup ion spectrum is also studied by direct numerical analysis.