On the basis of LMTO-ASA band calculation method, the electronic structure of (Ba_1-xK_x)BiO₃ system was obtained by using a virtual crystal approximation (VCA) in which the atomic sphere radii and potential parameters in different compositions are determined by linear interpolation. We contrast the composition dependence of the VCA electronic structure with those of the expended unit cell method. It is shown that the VCA method was valid for such a complex system. The accuracy of our LMTO-ASA-VCA results is also discussed.