Abstract: Based on the research of Lebuguolaji tunnel in the region of high seismic intensity of southwest China,seismic performance of the intersection of horizontal adit and main tunnel in expressway is studied by using Newmark implicit integral method and unified artifitical boundary.Results show that stress concentration of the intersection of horizontal adit and main tunnel is obvious,and the safety factors alternately change under earthquake action.The arch of the inersecion tends to be tension stress and is the weak part of the tunnel.The research may be as a reference to seismic design and construction of tunnels.