Abstract: The stabilities of underground facilities are the important research contents of geotechnical engineering. It is meaningful to improve the explosion resisting abilities of underground caverns for national defense and civil projects. So it has important strategic significance to carry out site explosion resisting tests on underground caverns. The displacement characteristics at the top of an underground cavern under three different conditions are introduced, that is long and close cables, short and close cables and regular cables . Furthermore, the situations that two kinds of base plates are used for cables to protect the displacement of the top of the cavern are compared. A conclusion that the protecting effects of flaring cup base plates are better than paddle base plates is put forward . This passage also analyses the relationship between the relative displacement at the top of the cavern divided by the span of the cavern and the scale distance of the explosion is analyzed. It is helpful for searching for the best protecting effects for practical projects.