Abstract: The resolution of an optical aperture synthesis telescope can be degraded by phase errors unless its subapertures are aligned to within a small fraction of the wavelength of incoming light. The phase diversity method can be used to estimate small misalignment errors of subapertures. This paper proposes a design of wavefront sensor of phase diversities by incorporating a GA (Genetic Algorithm). Such a design is suitable for detecting piston errors of an aperture synthesis telescope. Computer simulations are used to validate the algorithms and techniques, as the results show that this GA-based method can efficiently recover wavefront phases and thus detect piston errors.