The invention provides an image sensing device and an operation method thereof. The image sensing device at least comprises a pixel array and a read-out circuit, wherein the pixel array comprises a plurality of sub arrays, each sub array comprises i*j pixel units, i is the number of rows, j is the number of columns, i is larger than or equal to two, j is larger than or equal to two, control grids of the pixel units in the same row are connected with the same work line, drain electrodes of the pixel units in the same row are connected with the same control line, source electrodes of the pixel units in the same column are connected with bit lines, the pixel units in the sub arrays become light-sensitive under the action of voltage of predetermined word lines and control lines and generate output currents of the i*j pixel units, the output currents are output to the read-out circuit through the bit lines, and the read-out circuit is used for collecting and averaging the output currents and converting the averaged currents into voltage to be output to an external circuit. The image sensing device and the operation method solve the problem that exposure time of the pixel units is not uniform, lower shot noise of an image and improve the visual effect of the image.