The invention discloses a sensor and a manufacturing method thereof. The sensor comprises a substrate, a group of crosswise arranged grid lines and a group of data cables, and a plurality of array-shaped sensing units defined by the group of crosswise arranged grid lines and the group of data cables, wherein each sensing unit comprises a film transistor unit and a photodiode sensing unit, and the film transistor unit is bottom gate type; the photodiode sensor unit comprises a receiving electrode connected with a source electrode, a photodiode located on the receiving electrode, a transparent electrode located above the photodiode and a bias line located on and connected with the transparent electrode, and the bias line is parallel with the grid lines. Compared with the prior art, the manufacturing process disclosed by the invention reduces use quantity of masks, lowers manufacturing cost, simplifies a production process and greatly improves device productivity and yield of products.