Abstract: Interior reservoirs in the Xinglongtai Buried Mountain which locates at the central south of the Western Sag,the Liaohe Depression,the Bohai Bay Basin are highlights in recent domestic researches on buried mountain reservoirs.Meanwhile,they are also big challenges to current exploration methods and technologies.Geochemical studies on metamorphic rocks in buried mountain have been conducted based on their petrographic characteristics.It has been found out that major elements are rich in Si and poor in Fe and Mg.As to trace elements,P and Ti are poor and K and Pb are rich.∑REE is high with LREE enrichment,right-inclining normalized REE pattern and inconspicuous Eu anomaly.All these characteristics have indicated that original rocks of metamorphic rocks come from cognate upper crust and there is little possibility for transcrustal deep faults development.Protolith restoration shows that both ortho-and para-rocks exist in the buried mountain at the same time occurring as stratiform body.All the above mentioned results have big theoretical significance for guiding reservoir explorations in the burial mountain.