The invention discloses a sunlight tracking sensor. The sunlight tracking sensor comprises a tubular housing, the tubular housing is long-strip-shaped, the top portion of the tubular housing is provided with a light transmitting panel 2, the center of the light transmitting panel is provided with a square photomask, the photomask is projected in a square shadow region at the center of a circuit board at the bottom of the tubular housing, the center points of four edges of the square shadow region are each provided with a photosensitive tube superposed with the four edges in an attached mode, and the photosensitive tubes and four voltage comparators form a working circuit. The sunlight tracking sensor is simple in structure and low in cost. The tracking precision can be smaller than +/-0.05 DEG, the cross section is small, the sunlight tracking sensor and a reflective mirror heat collector form a three-point one-line arrangement, the shading is small, and the sunlight tracking sensor is especially suitable for sunlight tracking of a heliostat.