Abstract: As a classical image segmentation method, Otsu adaptive threshold algorithm has been applied widely in image processing. But the long-time computation limits the use of the two-dimensional Otsu threshold algorithm based on the Otsu threshold algorithm. This paper gives a fast algorithm for two-dimensional Otsu adaptive threshold algorithm that overcomes the disadvantage of computational complexity. This fast algorithm gets rid of redundant computation and yields a look-up table by iteration. The experimental result has demonstrated that the computational time of the fast method is not only far less than that of the original two-dimensional one, but also yields the same threshold as that of the original method.