Abstract: Xihu Trough located at east-north part of the shelf basin in the East China Sea, had long been short in these data available for deep strata and resulted in less possibilities of discussion on the source rock of deep strata. This paper puts forward some views about genetic mechanism of source rock within deep strata according to general laws of rift-basin evolution, new points of geological characteristics of Pinghu Fm. developed in postrift, and regional geologic data.