New Zhongliangshan tunnel on ChengduChongqing passengerdedicated railway crosses above existing Zhongliangshan tunnel on XiangyangChongqing railway, with the minimum vertical distance between the two tunnels being only 2.9 m. Numerical simulation and field tests are made so as to ensure the safety of the new tunnel and the existing tunnel. The study shows that the existing tunnel has an upward movement trend after the excavation of the abovecrossing tunnel; the maximum vertical displacement occurs at the tunnel crown, reaching 7.10 mm; the maximum horizontal displacement occurs at the spring line, reaching 1.73 mm; the maximum tensile stress appears at the inner side of the spring line; the maximum compressive stress appears at the inner side of the tunnel crown. Reinforcement measures for the existing tunnel is proposed and crown displacement monitoring points and horizontal convergence measuring lines are laid out according to the calculation results. The vertical displacement measured is close to the calculation value; the horizontal displacement measured is slightly less than the calculation value, but the regularity of the two values tends to be consistent. It proves that the research method is feasible and rational. 