According to three composite wave-plate theory and simulated annealing algorithm, a mica achromatic half wave-plate used in visible range is designed. Theoretical analysis shows that the retardation deviation of this device is within 2% covering the spectrum scope of 400～700 nm. This device has been measured over the visible range by normalized polarizing modulation measurement. The retardation deviation is within 4.8% based on the average equivalent fast axis. The retardation deviation of the device is within 2.9% based on the equivalent fast axis corresponds to the measuring wavelength. This mica achromatic half wave-plate can be applied in many fields.