Abstract: Based on relevant research results from investigation of existing loess tunnel works, the author has com? pared the advantages, disadvantages and applicability of various research methods, summarized some complex issues in loess tunneling and underground engineering and put forward relevant counter solutions, mainly including surrounding rock classification method reflecting mechanical principle of dynamic construction under complex geological conditions, spatial-temporal evolution law and calculation method of surrounding rock pressure at tunnel portal, influence of water softening mechanism of loess on stability and durability of tunnel structure, deformation law and structural optimization of surrounding rock when the tunnel passes through the loess-bedrock binary stratum, optimal design of waterproof and drainage system of loess tunnel, reinforcement and protection technology of side and front slopes in bridge-tunnel connection project, ecological restoration and other engineering scientific problems.