Multilayered magneto-impedance microsensors (Finemet/Copper/Finemet) were elaborated by microfabrication process using bi-layers lift-off method. A post-annealing step was carried out at 300°C for 1h under magnetic field, which led to induce a longitudinal or transversal anisotropy in the magnetic films. A method based on a double amplitude demodulation was proposed for the sensitivity characterization corresponding to the AC magnetic field measurement capability. According to these alternating magnetic field characterizations, the sensitivity, the linearity and the bandwidth of the microsensor were obtained. The highest sensitivity is around 4200 Ω/T and the measurable sensor bandwidth reaches up to 300 kHz. The sensor presented no hysteresis since a DC bias field larger than anisotropy field is applied.