Abstract: As petroleum strategic storages,unlined caverns for storage of oil need suitable hydrogeologic and engineering geological conditions.However,there are many bad geological bodies in the storage regions. They directly influence the hydrogeologic and engineering geological conditions in storage regions.In the paper,Jinzhou underground oil storages is considered as an example to analyze the altered rocks with expansibility in underground oil storages.There are many altered rocks in the region,and they belong to hydrothermal alteration by intrusion of basic dykes.The altered rocks have weak expansibility.It is found by disintegration test that the altered rocks can disintegrate.Through identification of minerals and rocks and X-ray diffraction analysis,it is found that clay mineral of the altered rocks is smectite.According to properties of the altered rocks with expansibility,the paper present control measures in the altered rock section during the construction of underground caverns for storage of oil.