A counting method, a counting device, and a counting system and a pixel array using the counting device are provided. The counting device includes a storage module, which comprises multiple storage units in cascade interconnection, the multiple storage units store a plurality of cumulative count values, the multiple storage units are configured as at least one group of storage units; an arithmetic module connected to a first group of storage units and a last group of storage units for calculation according to a received count value and an added cumulative count values input through the last group of the storage units so as to obtain a current added cumulative count values of corresponding objects, which is then output to the first group of the storage units in cascade interconnection.