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AbstractThe Nansha ultra‐crust layer‐block is confined by ultra‐crustal boundary faults of distinctive features, bordering the Kangtai‐Shuangzi‐Xiongnan extensional faulted zone on the north, the Baxian‐Baram‐Yoca‐Cuyo nappe faulted zone on the south, the Wan'an‐Natuna strike‐slip tensional faulted zone on the west and the Mondoro‐Panay strike‐slip compressive faulted zone on the east. These faults take the top of the Nansha asthenosphere as their common detachmental surface. The Cenozoic dynamic process of the ultra‐crust layer‐block can be divided into four stages: K2‐E21, during which the northern boundary faults extended, this ultra‐crust layer‐block was separated from the South China‐Indosinian continental margin, the Palaeo‐South China Sea subducted southwards and the Sibu accretion wedge was formed; E22‐E31, during which the Southwest sub‐sea basin extended and orogeny was active due to the collision of the Sibu accretion wedge; E32‐N11, during which the central sub‐sea basin extended, the Miri accretion wedge was formed and “A‐type” subduction of the southern margin of the north Balawan occurred; N12‐the present, during which large‐scale thrusting and napping of the boundary faults in the south and mountain‐building have taken place and the South China Sea stopped its extension.