Abstract: This paper presents a 3D edge detection algorithm based on Gaussian facet model.First we generalize the classic Haralick facet model and introduce the 3D Gaussian facet model using the Gaussian weighted least squares fitting,which uses spatial weights to express the relative importance of image samples in estimating model parameters.Then we employ the3D integrated directional derivative gradient （IDDG） operator to robustly estimate the gradient direction,and along this direction the zeros of the second directional derivatives are computed to locate the subvoxel positions of the surface points.Experimental results show our method can effectively reduce the interference of adjacent edge and can achieve good performance in extracting edge points of small structures.