Co64Fe4Si14.5B14.5amorphous ribbon was fabricated by the melt-spinning technique. Soft magnetic properties of the ribbon were improved by annealing at 623K for 1 hour with a zero magnetic field, a 50mT longitudinal or transverse external magnetic field comparing with the as-quenched ribbon. The longitudinally driven giant magneto-impedance (LDGMI) effect and its field sensitivity (ξ) have been investigated in the frequency (f) range of 1kHz~1MHz. It is found that at f=51kHz, the LDGMI effect and ξ reach the largest values for the sample annealed with a longitudinal magnetic field.