Abstract: Based on the thermal simulation of organic acid,rock section and cathodeluminescence,we analysed the relationship between the coal source rocks and the quartz overgrowths in the coal source rock of Shanxi Formation of the eastern Ordos Basin.The research results indicate that the Ⅲ-kerogen from oxygenic clusters collapsing can produce more organic acids in the thermal simulation.While in the acidic pore environment,the experiment of rock section and cathodeluminescence shows that a large amount of organic acid dissolved unstable minerals such as volcanic debris and feldspar from quartz sandstone and debris quartz sandstone and new SiO₂ that occurred in precipitation provided the source of quartz overgrowths.Accordingly,the existence of organic acid can cause quartz overgrowths and finally tight sandstone formed.