Topology optimization is a high level optimization method of structural optimization, which is a focus study of engineering field. But there is no research achievement in topology optimization of tunnel engineering. In this paper, tunnel model of topology optimization is established; topology optimization analysis on tunnel cavern is made with high-level topology optimization theory; and pre-strengthening support theory is put forward, which is three-layers support combined with primary-supporting and inner lining and strong support on wall rock. The place of pre-strengthening support is found out by the analysis of topology optimization. It shows that this method is reasonable and effective and can be used as reference in the construction and design of road tunnel.