A detector pixel, an array substrate, an apparatus and a method for detecting an intensity of a ray are provided. The detector pixel includes substrate, first transistor, second transistor, storage capacitor, photosensitive element, first control line, second control line, first data line and second data line. The first and the second transistors are dual-gate transistors; the first transistor has a bottom gate connected to the first control line, a top gate connected to the second control line, a first electrode connected to the storage capacitor, and a second electrode connected to the first data line; the second transistor has a bottom gate connected to the second control line, a top gate connected to the first control line, a first electrode connected to the storage capacitor, and a second electrode connected to the second data line; and the storage capacitor is connected to the photosensitive element.