Due to their high Curie temperatures (Tc), wide band gaps and large magnetic moments, Co-based Heusler alloys with high spin polarization are good candidates for spintronic applications [1]. Among this group, Co2FeAl is a typical full-Heusler alloy. However, the Fermi level (EF) of Co2Fe-Al is almost at the edge of the gap, leading to the instability of the half-metallic properties. In order to obtain the wider band gaps, larger magnetic moments and other properties which are preferred by Heusler alloy application, understanding and manipulating the electronic and magnetic properties of Heusler alloys are of vital importance. In this work, we focus on the enhancement of the stability, magnetic moments and the width of the gap in the minority spin channel by doping GeTe into Co2FeAl Heusler alloy.