We grew a CoFe thin film on the surface of Co based amorphous ribbon (Co66Fe4NiSi15B14) to investigate the effect of this coating on giant magneto impedance(GMI). We investigated GMI over a frequency range of 120 kHz~3 MHz and under a static magnetic field. The results show that GMI for amorphous ribbons can be enhanced by this coating process .The study found that surface roughness effect on the GMI when skin effect is significant. The very large enhancement of the GMI value is a consequence of reducing the sample surface roughness，reducing the influence of the surface demagnetizing field and the closed magnetic flux path under the CoFe film layer.