The FID arising from the quadrupole interaction is broken into a rotational echo train under the slow rotation condition, and the number of these echoes increases when adjusting the angle between the rotational axis and the applied magnetic field towards the Magic Angle. Thus, a accurate and quick setting of the Magic Angle in MAS-NMR experiments can he easily obtained by this phenomenon. It is theoretically explained by analysing the FID of a spin-1 system. The setting accuracy within 0.05°with a per-deuterated HMB sample is experimentally demonstrated.