Used in the city subway, underground tunnels are taken to two equal sections [1], only meeting special engineering needs it is designed with two unequal sections, for example crossover, contact lines and stop (deposit) car line and so on. The tunnel with parallel non-large section has carried out preliminary research. Through the establishment of a numerical model [2], the influence of the supporting mechanical behaviour and stability of the surrounding rock of an unequal span highway tunnel have been analysed; also, construction mechanics and surface settlement of a double line tunnel with antisymmetric sections have also been studied [3], however further study is still needed.