The stable ordered structures of (GaAs)1-xGe2x system have been studied, using the probability wave theory of the atomic configuration (PWAC). Based on the determination of the ordered structures, the electronic structures of five typical stable ordered structures for x = 0.5 are investigated by the use of first principle self-consistent LMTO method. The calculated results show that the electronic properties of different ordered structures can be quite different. The more Ga-Ge and Ge-As atomic bonds in unit cell of ordered structures are, the more possible the ordered structures are expected to exhibit a metallic character.