A simple atomic structure model was proposed for Ga1−xInxAs solid solution. Distortion energy caused by the differences in Ga‐As and In‐As bond lengths was calculated using the valence‐force‐field approach. Calculated bond lengths for Ga1−xInxAs agree well with the extended x‐ray absorption fine structure data. The calculated mixing enthalpy which corresponds to the excess energy caused by distortions agree with that from phase diagram.