Abstract: Disclosed in the present invention is An annotation method of arbitrary-oriented rectangular bounding box, wherein: the elements for annotation being: the coordinates of the center point C, a vector {right arrow over (CD)} formed by the center point C and a chosen vertex D, and the ratio of the vector {right arrow over (CP)} to vector {right arrow over (CD)}, where {right arrow over (CP)} is the projection of the vector {right arrow over (CE)} to {right arrow over (CD)}, and {right arrow over (CE)} is a vector formed by the center of the bounding box to one of the vertex E that close neighbor to vertex D; and it is also required that the vector {right arrow over (CP)} is in the same direction as the vector {right arrow over (CD)}, the vertex E in either of the clockwise or counterclockwise direction of the vertex D.