The support generation technique in some rapid prototyping manufacturing process plays an important role in fabricating parts of overhang geometry structures and guaranteeing the part fabrication process smoothly. A new robust and automated support generation method is proposed based on slice in this paper. During the support generation process, the self-support of part and the self-support of the support structure itself are designed to save support material. Furthermore, the different contour offsetting method corresponding to different toolpath generation method (offset toolpath generation and Zigzag toolpath generation) is also proposed to separate the part and the support structure so that the support structure can be removed easily.