Double-track railway over-cross tunnels were stuied by numerical simulation and regression analysis. A series of research on the influence of the construction of newly built tunnel to the existing one in different surrounding rock grades was carried out. According to the numerical simulation, 48 mechanical models were established, which considered various clearance, rock conditions and different construction sequences（building above or beneath existing one）. Based on regression analysis on the calculation results from the 48 models, the deformation prediction formulas for the existing tunnel's surrounding rocks and ballast bed were deduced. According to the high-speed rail allowed standard of roadbed deformation during operation, the minimum clear distance value by which the existing tunnel's operation would not be affected was recommended. Some analysis on the surrounding rock pressure's variation of the existing tunnel caused by new tunnel construction was done. Taking the variation amplitude as the evaluation criteria, a critical value of influenced clearance for railway over-crossing tunnels project is provided. Meanwhile, the results found that the tunnel cross the building had a smaller impact on itself compared with that of the tunnel which goes through the building.