Abstract: Based on the research of organic macerals and their occurrence state in marine shale of southern Lower Paleozoic, according to the characteristics of the nano-pores of organic matter showed by the 2D image of the field emission scanning electron microscopy(SEM), the genetic types of nano-pores of organic matter in Longmaxi Formation shale in Sichuan basin are classified into bituminite spherulite pores, gas pores and mold pores. The cause, morphology, size, evolution, connectivity, interrelationship and their roles in shale reservoirs of these three kinds of nano-pores are discussed respectively. Research shows that the maceral of Longmaxi Formation shale are mainly bituminite. Both bituminite spherulite pores and gas pores are developed in the interior of the bituminite, formed during the degradation of organic matter and thermal evolution, which is a strong evidence and prior space for shale gas formation, adsorption and accumulation. In the organic-rich shales at the bottom of Longmaxi Formation, various nano-pores of organic matter are highly developed, which directly reflect strong gas-forming and gas gathering effects.