The control of stability of surrounding rocks is difficult during construction of large crosssection soft rock tunnel. A numerical model of Guchengling Tunnel on BaojiLanzhou Passengerdedicated Railway is established based on surveying and design data, construction technology and monitoring data. The deformation characteristics of large crosssection soft rock tunnels are analyzed and the influence of invert arch step distance and bench length on stability of large crosssection soft rock tunnels is revealed. The numerical test results are regarded as guidance for construction of large deformation section of Guchengling Tunnel, the accumulated deformation of primary support has been reduced by 70%.