Abstract: The Huizhou 21 structure, a drape structure over a buried hill, is a key area for oil exploration in the Huizhou Sag of the Pearl River Mouth Basin. However, the Huizhou 21 oil and gas field is the only one discovered in the middle and shallow layers, no commercial hydrocarbon discoveries have been detected so far in the deep. As we know, the analysis of structural evolution of the buried hill is the key to deep-layer oil exploration. Based on seismic data and drilling results, using the balanced geological profiling as a tool, the geological structure and tectonic evolution process of Huizhou 21 buried hill and the influence of tectonic evolution process on hydrocarbon accumulation are carefully studied in this paper. It is found that the Huizhou 21 buried hill tectonic belt has experienced four stages of evolution: magmatic intrusion and granite basement emplacement in Early Cretaceous, volcanic eruption in Paleocene, uplifting and differentiated faulting in Eocene and getting into shape in Oligo-Miocene. The control of tectonic evolution over deep reservoir formation is mainly manifested in three aspects: the reformation of volcanic reservoir, the development of sedimentary system in rifting period and the migration and accumulation of oil and gas. There are high quality and large scale reservoirs in the Wenchang and Shenhu Formations of the study area, and they are important oil exploration targets in the deep.