There are two ways of the control of groundwater on secondary migration and accumulation of oil and gas. One is macroscopic control and the other is microscopic control. The macroscopic control refers to the effects of regional groundwater flow in basins on migration and accumulation of oil and gas. It determines the direction of regional migration and main accumulation regions of oil and gas. The microscopic control refers to the effects of groundwater on migration and accumulation of oil and gas in traps or reservoirs. It decides the relations of groundwater and the geometry and lithology of traps and reservoirs with the formation, preservation and destruction of oil and gas traps and reservoirs. The paper discusses the macroscopic and microscopic control of groundwater on migration and accumulation of oil and gas and its study methods.