In this paper, the effect of sample length on different currents and frequencies of measurement on magneto impedance (MI) of amorphous cobalt based ribbons was investigated. Firstly, we cut the ribbon to 4 cm length and then measurements of MI were carried out in constant current of 8 mA and frequency ranges between 1 to 15 MHz. The maximum sensitivity (9.16 Oe-1) at a frequency of 11 MHz was obtained. Also, the maximum extinction field was obtain 41.6 Oe. In the next step, the currents of 6 to 14 mA and the frequencies from 1 to 6 MHz were examined and in the optima conditions the maximum MI reached to 195%. In the next step, the length of ribbon was reduced to 2 cm and the MI was measured at previous currents and frequencies that results showed the reduction of MI in the most of conditions. In addition, at frequency ranges between 1 to 15 MHz, the maximum sensitivity was 10.2 Oe-1 and the maximum extinction field was 52.3 Oe. As a result, by decreasing the length of the ribbon, the MI reduce, but the sensitivity and excitation field increases, which is suitable for sensing applications. This behavior can be explained due to the demagnetization field, which is strongly dependent on the sample length.