A method and a device for objects counting in image processing includes acquiring the depth image of any one frame; detecting objects according to the depth image; associating the identical object in different frames to form a trajectory; and determining the number of objects according to the number of trajectories. The devices include an acquisition module for acquiring the depth image of any one frame; a detection module for detecting objects according to the depth image; an association module for associating the identical object in different frames to form a trajectory; a determining module for determining the number of objects according to the number of trajectories. The objects are detected according to the depth image. The identical object in different frames is associated to form a trajectory and the number of objects is determined according to the number of trajectories.