Abstract: Based on the complexity of the structure， the paper presents the concept of subtle structure. It refers
to those whose characteristics and evolution history can not be identified owning to the limitation of exploration
technology and the complexity of the structure itself. The study of the subtle structure should be based on the iden-
tification of its interface and signs of deformation， and focused on analysis of the stratigraphic structure guaranteed
by advanced tectonic thinking and technological means. Lots of subtle structural styles form in the deep Jiyang De-
pression. These styles are strike slip fault zone， deep Jiyang development of large-scale strike-slip faults， inversion
structures， structural transform zone， diapir structure belt， buried hill structure and buried fault， i. e.. The explo-
ration for buried hill can be explored along strike-slip fault. Identification of hidden structural styles are guidance
and reference for expanding new areas of deep oil and gas exploration， optimization and evaluation of favorable oil
and gas accumulation zones， and further oil and gas comprehensive geological study.

Key words: Jiyang Depression, subtle structure, buried hill exploration, Structural style, Wanggu I