Two field-of-view shifted Shack-Hartmann wavefront sensors (FSWFS) are proposed, which are used to measure the wavefront information of object signal under daytime conditons. The experimental results on the sky background's non-uniformity characteristics are obtained, the detecting error of the dual focal-plane FSWFS is analyzed in this paper and its principle has been proven by experiments with a single focal-plane array. The measuring results indicate that FSWFS can precisely and stably measure the wavefront information of object signal with strong background. At the same time, the detection capacity of FSWFS is estimated and its restraining factors are analyzed, and the estimation results show that the adaptive optics system with FSWFS in Yunnan observatory can precisely measure the wavefront information of object signal whose V magnitude is 5 when the brightness of the sky background is 10 W/m2·sr.