Abstract: In order to find the reasonable distance of large section tunnel under loose and soft surrounding rock condition, we use elastic-plastic mechanical analysis and numerical simulation to comprehensively analyze tunneling displacement field, stress field and fracture field in different spacing. Studies show that with the increase of tunnel distance, the displacement of roadway sides and roof and floor is decreased, then the rate of the displacement is reduced, and the interaction between the two tunnels becomes less. The stress distribution around the tunnel is gradually regular. The displacement vector field is smaller, and the changed rate is significantly reduced; the plastic inter-zone of two tunnels becomes less, the interference of the tunnels reduced after spacing of 40 m.