Abstract: Most researches related to loess mechanical properties highlight loess foundations and slopes, while little attention has been paid to loess tunnels. Several typical characteristics of loess both as a special soil and surrounding rock of loess tunnels, such as sensitivity to water content, failure at small strain, anisotropy, loess joints and its impact on stability of loess, are studied from the perspective of stability of tunnel and underground engineering. It is concluded that the existing methods and results associated with mechanical behaviours of loess can’t take the actual characteristics of loess into account when the loess behaves as surrounding rock of deep-buried tunnels. The necessary tests and corresponding methods are suggested mainly aimed at the surrounding rock classification of loess tunnels.