Abstract: Considering the insider and unknown attack, to further improve the efficiency, an intelligent-efficient method for generating the optimal penetration path is put forward. Firstly, we define the two-layer threat penetration graph(TLTPG), where the lower layer is called host threat penetration graph(HTPG) and the upper layer is called network threat penetration graph(NTPG). Then, based on knowledge graph, we build the host resource knowledge graph(HRKG), which is used to generate the HTPG intelligently and efficiently. Further, utilizating the HTPG, we design the NTPG generation algorithm based on penetration information exchange. Finaly, we describe the algorithm of optimal penetration path generation by using the TLTPG. Experimental results show that the proposed method can improve the efficiency of generating the optimal penetration path under the condition that the insider and unknown attack are considered.