Most of current segmentation algorithms in H.264/AVC compressed domain lose the local Motion Vector (MV) field and have high time complexity because of global motion compensation. A new fast segmentation algorithm, called Convex Hull segmentation in Spatial-Temporal Filter (STF) based on Boundary Search on compressed domain (BS-CHSTF) was proposed. Motion vector field in bit stream was mainly used in this algorithm. Firstly, the STF algorithm was used in preprocessing the MV, and then eight-direction adaptive search algorithm was used to get connected region, which is filled by constructing the convex hull using boundary of the connected region. Afterwards, multiple connected regions were clustered by redefining the distance between connected regions distance. Finally, the motion object segmentation was obtained by optimizing the mask. Compared with Gaussian Mixture Model (GMM) segmentation algorithm and Ant Colony Algorithm (ACA), the experimental results show that the segmentation accuracy is improved about 3% averagely, and even in the case of lack of motion vector field, the segmentation accuracy increased nearly 20%, while the segmentation speed increased an average of nearly 25%. The method focuses on obtaining the moving object quickly with better segmentation accuracy even in the case of Moving Object (MO) uncompleted.