Abstract The energy bands of GaAs, GaP and GaAsxP1-x are calculated using the zone-variational method. Since there are different atoms in a cell, different radii are selected for various atomic spheres according to the actual size for corresponding atoms. The crystal potential is calculated by superposing various atomic potentials. Since the atomic potentials are distorted in the bonding sphere under the interaction with other atoms in crystal, a few adjusting parameters are selected to adjust the corresponding atomic potential and an analytical expression is used to approach the resulted potential. The potential adjusting parameters are selected to make the calculated energy band close to experimental results. The band structures which agree with experimental results are obtained for GaAs and GaP. Furthermore, these poteatials are used to calculate the energy band of GaAsxP1-x.