The invention provides a wavefront sensor used for a solar self-adaptive optical system. The wavefront sensor comprises a collimator (1), a narrow-band light filter (2), a sampling reflector (3), a relay system (4), a beam expander (5), an attenuator (6), a phase shifter (7), an acquisition device (8) and a data processing module (9), wherein the solar radiation intensity uniformity and half-wave loss phase shift principle are utilized, and the defects that in a traditional solar self-adaptive optical system, a relevant Hartmann-shank wavefront detection technique is low in detection space resolution, low in long-scale contrast expansion object wavefront detection precision, large in wavefront detection calculation quantity, relatively lower in efficiency and the like are overcome. The wavefront sensor is simple in optical structure, small in calculation quantity, rapid in wavefront detection and processing speed, high in detection efficiency and not high in contract requirements on objects on a sun surface action area, and thus the wavefront sensor can be used for wavefront measurement on long-scale contrast expansion objects under the condition of middle and even low poor seeing degree condition, the correction bandwidth of the solar self-adaptive optical system is effectively improved, the working interval is expanded, and the correction effect is improved.