On August 21, the world's longest heavy-haul railway tunnel, Xiaoshan Tunnel of the Menghua Railway, designed by the China Railway Fourth Survey and Design Institution, was successfully holing-through. Being the longest heavy-haul railway in the world, the main line of the Menghua Railway is 1814.5 kilometers long. The Xiaoshan Tunnel is designed as two single-hole structures, the left line is 22.751 kilometers long. It is the longest heavy-haul railway tunnel in the world. By using the methods of remote sensing interpretation, complex geophysical prospecting, in-situ testing, large-scale geological survey and mapping, more than 20 schemes of 4 series have been selected in detail before and after the study. four series of more than 20 schemes were selected in detail before and after the study，and finally choose the best scheme.