For the daytime adaptive optics system, a field-of-view shifted Shack-Hartmann wavefront sensor (FSWFS), which is used to measure the aberrant wavefront under daytime conditions, is proposed. Because the field angle of the object signal in adaptive optics systems is much less than that of the sky background, the effective object signal is separated from the strong sky background. Experimental results indicate that FSWFS with a single focal-plane array can precisely and stably measure the aberrant wavefront information with a strong sky background under daytime conditions.