Based on studies of the types and distribution of lavas erupted during the Tertiary in Shengli Oilfield, the influence of volcanic activities on the generation of hydrocarbons is discussed, with the Dongying depression an d Yucheng depression as examples. It is concluded that weak volcanic activities do not aff ect the generation of hydrocarbons, but may change the characters of crude oil t rapped before the eruption. This understanding is helpful to the research on th e petroleum trapping mechanism in basins containing volcanic rocks