To study the effect of multi-arc tunnel construction on existing structures in jointed rock mass, Yuzhong connecting tunnel which locates in Chonqing, China is selected as a research object. A numerical model is established, and the two-dimensional discrete element analysis software UDEC is used, since it can reflect the influence of jointed rock mass. The settlement of tunnel crown, the foundation settlements of upper buildings and the deformation and stress characteristic of metro Line 6 caused by tunnelling are highlighted. In addition, the monitoring data are also analysed and compared to the results calculated by UDEC. The results of numerical analysis indicate that most of the settlements of tunnel crown and building foundations are caused by the excavation of upper bench in the left tunnel. The maximum settlement is 3.81 mm with the maximum slop of about 0.02%. Both the settlement and the slope are within the range of the upper buildings, allowable change. The tunnel spandrel of metro Line 6 heaves upwards due to the loss of ground during the excavation of the new tunnel, and the bending moment of Line 6 distributes similarly with its deformation curve. The maximum bending moments is 238 kN·m which locates in the tunnel spandrel and is within the typical capacity of the lining. Generally, the numerical results are in accordance with the monitoring data, which shows that UDEC can accurately reflect the effect of tunnelling on existing structures in jointed rock mass.