Electronic structures and magnetic properties of Mn2Co1−xCrxAl are investigated. Mn2Co0.75Cr0.25Al and Mn2Co0.25Cr0.75Al are half metals. Half-metallicity of Mn2Co0.25Cr0.75Al is destroyed once the disorder appears. Half-metallicity of Mn2Co0.75Cr0.25Al still be maintained in all kinds of disorder.