Abstract: By full use of a variety of technical means such as drilling core observation, thin sections analysis, scanning electronic microscope and energy spectrum analysis, the article analyzed the petrological characteristics of the reservoirs in the East Depression of the North Yellow Sea Basin and discussed the impact of hydrothermal activity on the reservoir. The research suggests that the solution fissures in the reservoir in the Depression are filled with authigenous minerals related to hydrothermal activity that damages the sandstone reservoir. It is found that in the Mesozoic strata of the North Yellow Sea Basin, there were heat anomalies and hydrothermal activities related to magmatism, and existed the geological background of hydrothermal activity related to magmtism. The hydrothermal activities are found in different stages, mainly in the Late Jurassic. The hydrothermal activities usually have close relation with faults.