This paper summarizes the new results on the petrogenesis of Mesozoic granitoids and volcanic rocks in South China.The authors propose that these rocks were formed in time and space as a response to regional tectonic regime change from the continent-continent collision of the Indosinian orogeny within the broad Tethyan orogenic domain in the Early Mesozoic (T1-T3) (Period Ⅰ) to the largely extensional setting as a result of the Yanshanian orogeny genetically associated with the NW-WNW-ward subduction of the paleo-Pacific oceanic lithosphere in the Late Mesozoic (J2-K2) (Period Ⅱ).