Abstract: This paper proposes an auto-adaptive threshold method of two-dimensional（2-D） histogram based on Multi-Resolution Analysis（MRA），decreasing the calculation complexity of 2-D histogram whereas improving the searching precision of multi-resolution threshold method.Such method originates from the extraordinary segmentation effects achieved by 2-D histogram threshold segmentation method through the spatial correlation of gray level and the flexibility as well as efficiency of the threshold searching of multi-resolution threshold segmentation method.Experiments results demonstrate that such method can obtain segmentation results similar with the exhaustive 2-D histogram method，whereas the calculation complexity decreases exponentially with the increase of resolution level.